Method for coating surfaces and use of the articles coated using said method

ABSTRACT

A method for electroless coating of substrates by applying an activating coat of polyelectrolyte or salt with a first aqueous composition; rinsing the activating coat such that the activating coat not being entirely removed; contacting and coating of the activated surfaces that have remained after rinsing with an aqueous composition in the form of a solution, emulsion or suspension, to form an organic secondary coat; and drying. The activating coat is a solution, emulsion or suspension containing a anionic polyelectrolyte or at least one anionic salt in solution in water. The aqueous composition forming the secondary coat has constituents which can be precipitated, deposited or salted out and which are anionically, zwitterionically, sterically or cationically stabilized. The dry film formed in the process, comprising the activating coat and the secondary coat, has a thickness of at least 1 μm.

This application is a §371 of International Application No.PCT/EP2011/065764 filed Sep. 12, 2011, and claims priority from GermanPatent Application No. 10 2010 040 651.1 filed Sep. 13, 2010.

All of the documents cited in the present application are incorporatedby reference in their entirety into the present disclosure.

The invention relates to a method for coating surfaces, to acorresponding coating, and to the use of the objects coated by saidmethod.

Numerous techniques exist for generating homogeneous coatings onsurfaces, especially metallic surfaces, and preferentially by means ofdipping processes. The compositions used in such techniques,particularly for the production of anticorrosion coatings, primercoatings and/or electrodeposition coats, are compositions consistingprimarily of an organic matrix and/or of organic and/or inorganicadditive components, and the technologies utilized are preferably asfollows: in order to generate coatings which are very impervious,anticorrosion coatings with a dry film thickness of at least 3 μm aredesired, which are applied as thickly as possible in one process step.Anticorrosion coatings of these kinds may be used in particular asprimers or as an electrolessly applied deposition coating, particularlyin the form of a dispersion, which is utilized like an electrodepositioncoating.

PRIOR ART

The conventional electroless processes are based on the utilization ofthe rheological properties of the formulations used, to achieve completecoating of a workpiece. Although the accumulation of coating material atcritical locations can be reduced by continuously rotating the workpiecein question after the dipping operation, that technique does not allow ahomogeneous coating with a uniform thickness to be obtained. The reasonis that, during the drying and/or crosslinking operation, at locationswith relatively high proportions of coating, defects such as blistersand pops may occur, adversely affecting the quality of the overallcoating.

The electrophoretic processes avoid these problems by using electricalcurrent, with charged particles that are dispersed or colloidallydissolved in liquid undergoing migration in the electrical field. Inthis way, success is achieved in depositing a uniform coating bydipping, and in applying, for example, an electrocoat. The production ofhomogeneous coatings on metallic workpieces is accomplished by thistechnique. The coatings deposited exhibit extremely good adhesion in thewet state to the metallic substrate, allowing the workpiece to behandled without detachment of the coating in a downstream rinsing step.As a result of this, the amount of aqueous composition and the coatthickness of the resultant coating can be applied uniformly, even inworkplace depressions and locations that are difficult to access, andhence it is possible for fewer defects to occur during the dryingoperation.

With all of these processes, an excessive amount of liquid of aqueouscomposition may accumulate in depressions and may be transferred to thedownstream process step. The electrophoretic processes have thedisadvantage that, in addition to the amount of electrical energyrequired and in addition to suitable dipping baths, leading to anincrease in the costs, there are also instances of edge holidays, sinceelectrical fields are built up unevenly at edges, and the edges arecoated non-uniformly and possibly even incompletely. Moreover, cavitiesought to be avoided in the construction of the workpieces, since atthese locations an effect occurs which is comparable with the Faradaycage phenomenon. Owing to the reduced electrical field strength at suchlocations, insufficient for depositing an adequate amount of solids insuch areas, either no coating is formed on the workpiece, or the coatingthat is formed is of substantially lower thickness, particularly atundercuts (throwing power problem), leading to a marked impairment inthe quality of the coating. Additionally, in the case of electricaldeposition coating, such as for a cathodic electrocoat, for example, theelectrophoretic processes have the following disadvantages: acorresponding dip bath, together with all of the electrical andmechanical installations for temperature control, power supply, andelectrical insulation, with circulating means, with addition means, andbefore the disposal of the anolyte acid formed in the course ofelectrolytic coating, and with ultrafiltration for paint recovery(recycling), and also with control devices, has a very costly andcomplicated construction. The operating regime involves a very highlevel of technical complexity, not least on account of the high currentstrengths and energy quantities, in evening out the electricalparameters over the volume of the bath, in the precise setting of all ofthe operational parameters, and in the maintenance and cleaning of thesystem.

The known autophoretic processes are based on electrolessself-deposition, wherein, in a pickling attack, metal ions are removedfrom a surface, particularly a metallic surface, and wherein theconcentration of ions, such as of divalent, cationic ions, for example,such as, more particularly, of iron ions and/or zinc ions at theresultant interface, results in precipitation and/or deposition of anemulsion and/or suspension. Although the autophoretic processes do nothave the disadvantages of the electrophoretic processes in terms of theFaraday cage effect, the coatings produced in the known autophoreticprocesses have to be fixed after the first activating step, in a costlyand inconvenient multistage dipping process. Moreover, the picklingattack leads to an unavoidable contamination of the active zone,particularly of a dip-coating or spray-coating system, with metal ions,which must be removed from the affected zones using, for example, an ionexchanger. Moreover, the technique is based on a chemical depositionprocess which is not self-regulating and cannot be discontinued as andwhen required, such as by switching off the electrical current in thecase of the electrophoretic processes, for example. Accordingly, onprolonged residence time of the metallic substrates in the active zones,the development of an excessive coat thickness is unavoidable.

It is a long-pursued desire to form a coating of very great homogeneityand extremely uniform thickness in a dipping process, efficiently andcost-effectively, with an aqueous composition such as a dispersion or apaint formulation, in an extremely simple production process. The reasonis that to date there has been a lack of extremely simple methods forforming such an organic coating, in which a coating is depositedelectrolessly in one process step and, after drying, has a dry filmthickness of more than 5 μm, without any ions removed from the substratematerial being used to form the secondary coat. Furthermore, themulti-metal capacity represents a further distinguishing feature of thepresent invention. In that case the ions removed are in fact used, butan activating coat applied beforehand is not.

PROBLEM

The problem which exists is therefore that of proposing a method bywhich organic coatings can be generated on surfaces, especially metallicsurfaces, in an electroless deposition process, via a liquid system,said coatings being developed in a rinse-resistant form as and whenrequired. For this purpose, preferably, a dispersion and/or paintformulation is to be used as an aqueous composition. The coating is tobe applied extremely homogeneously and with maximum surface coverage. Itis to be deposited simply in—as far as possible—one process step. Itwill be advantageous if in such a method it were possible to apply acoating producing a dry film of at least 8 μm or at least 10 μm inthickness. It would also be advantageous if this coating were able toserve as a replacement for an electrocoat. A further problem was that ofproposing an extremely simple multistage method for producing thecoating.

SOLUTION

The problem is solved

with a method for electroless coating of substrates, comprising orconsisting of the following steps:

-   -   I. provision of a substrate,    -   II. optional cleaning of the substrate,    -   III. application of an activating coat of polyelectrolyte and/or        salt with a first aqueous composition (=activating agent),    -   IV. optional intermediate drying of the activating coat,    -   V. rinsing of the activating coat, the activating coat not being        entirely removed,    -   VI. contacting and coating of the activated surfaces that have        remained after rinsing, with an aqueous composition in the form        of a solution, emulsion and/or suspension, to form an organic        secondary coat (=precipitation coat),    -   VII. optional rinsing of the secondary coat, and    -   VIII. optional drying of the secondary coat,        wherein an activating coat is formed with an aqueous activating        agent in the form of a solution, emulsion and/or suspension        which comprises a) at least one cationic polyelectrolyte and/or        at least one cationic salt in solution in water, or b) at least        one anionic polyelectrolyte and/or at least one anionic salt in        solution in water, wherein the aqueous composition to form a        secondary coat has constituents which can be precipitated,        deposited and/or salted out and which are anionically,        zwitterionically, sterically and/or cationically stabilized,        where anionically and cationically stabilized constituents in        the aqueous composition do not adversely affect one another, and        wherein the dry film formed in this procedure or subsequently,        comprising the secondary coat or comprising the activating coat        and the secondary coat, has a thickness of at least 1 μm,        and the methods and uses described later on below, and also the        preferred and/or advantageous embodiments thereof.

DEFINITIONS OF TERMS

For the purposes of the present invention, the term “and/or” includesnot only any particular element but also all combinations of theelements recited in the listing in question.

For the purposes of the present invention, all quantity figures, unlessotherwise indicated, should be understood as figures by weight.

The term “solids and active ingredients” indicates that as well as thesolids that are firmly present in a liquid composition there may also beother substances present, which here are called active ingredients andwhich become solids only as a result of a chemical reaction or ofchanges in chemical and/or physical conditions, and which thereforeparticipate, for example through their bonded chemical groups, in theformation of a solid coating.

For the purposes of the present invention, the term “room temperature”denotes a temperature in the range from 15 to 28° C.

The term “pretreatment” denotes a treatment (=contacting of the surfacesthat are to be coated with a composition, typically a liquidcomposition), to which subsequently, optionally after subsequentcoating, a further coating is applied, such as at least one paint, forexample, for the purpose of protecting the coat sequence and the object.

The term “solution” also embraces colloidal solutions in the sense ofthe description given under the heading “Colloid chemistry” in the RömppLexikon Chemie chemical dictionary.

The term “electroless coating” in the sense of this specification meansthat for the coating of substrates with a composition comprisingsolution and/or dispersion (=suspension and/or emulsion)—in contrast tothe known electrophoretic methods—to form an activating coat and/or asecondary coat, either no electrical voltage is applied from the outsideor, in the case of a largely electroless embodiment of the coating, asmall electrical auxiliary voltage is applied, which assists the methodand possibly improves the coat that is formed in the method, but doesnot initiate precipitation or reaction.

The term “surface(s) to be coated” for the purposes of thisspecification denotes surfaces of objects, and especially of metallicand/or organic objects, which may have been precoated optionally, forexample, with a metallic coating such as a coating based on zinc or zincalloy, for example, and/or with at least one coating of a pretreatmentor treatment composition based for example on chromate, Cr³⁺, complexfluorides, Ti compounds, Zr compounds, silane/silanol/siloxane,polysiloxane, organic polymer/copolymer and/or reaction productsthereof. In certain embodiments surfaces of metallic and/or organicobjects and/or materials are coated on the same component and/or insuccession or simultaneously in the same unit. In the case of a singlevehicle body, for example, plastics surfaces and metallic surfaces mayoccur at the same time, and/or metallic surfaces made of differentmetallic materials may occur at the same time, such as of steel,galvanized steel and/or aluminum alloy, for example. It is also possiblefor a mix of different materials to be coated in one coating unit.

The term “silane” also embraces the resultant silanols and siloxanes,and hence the term “silane/silanol/siloxane” is used as well. Whereassilanols form in contact with moisture and water, siloxanes may formfrom them in water and on drying.

The term “activating coat” for the purposes of this specificationrelates to the coating which is formed with the activating agent, in thewet, dried and/or crosslinked state. This includes the wet film of theactivating agent, of the partially dried film, of the fully dried filmand of the film dried, if desired, at elevated temperature, of theoptionally chemically modified film, of the film optionally fixed with afixing aid, and of the film optionally crosslinked further byirradiation and/or thermally. Activating substances used in theactivating agent are, in particular, polyelectrolytes and/or salts.

“Activating” refers to the capacity, in a downstream method step such asa dipping step, for example, to cause a stable aqueous solution and/ordispersion, close to the surface of the activating coat, to undergoprecipitation, salting out and/or precipitation of activatingsubstances. In the context of the method of the invention, this is aprerequisite for a secondary coat to be able to be formed on theactivating coat, on the remaining activating coat and/or on thesubstrate freed largely or partially from activating agent.

The term “polyelectrolytes” in the context of this specificationdescribes water-soluble, anionic or cationic compounds, usually of highchain length, which may contain a chain, a backbone and/or a dendrimer,more particularly in the form of branched and/or linear polymers and/orcopolymers, and which may have molecular weights in particular in therange from 200 g/mol to 20 million g/mol.

The terms “latently anionic” and “latently cationic” denote ionicbehaviors which are partially concealed and/or which occur temporarily.This includes substances having strongly polarizing groups such asalcohols, which, although not ionic by definition, may initiate aprecipitation in the sense of the specification, such as polyvinylalcohols or polyethylene glycols, for example.

The terms “permanently anionic” and “permanently cationic” denote ionicbehaviors which occur and/or are apparent. Apparent here, for thepurposes of this specification, denotes compounds or atoms which possessions or which are per se such an ion (e.g., metal salts). Generallyspeaking, in the present text, no distinction is made between latent andpermanent behavior.

The term “rinse-resistant” for the purposes of this specification meansthat under the conditions of the respective unit and method sequence,the last coating in each case, such as a) an activating coat and/or b) asecondary coat, for example, is not removed entirely by a rinsingoperation (=rinsing) and hence in the case of a) its activating effectfor the subsequent coating or in the case of b) the secondary coatproduced by precipitation, coagulation, salting-out and/or deposition,is not removed entirely. In this way it is possible, for example, toproduce an optionally dried coating, preferably an impervious coating.

The terms “precipitation” and “precipitation reaction” for the purposesof this specification describe chemical reactions in which the reactantsare present in dispersion and/or solution in a solvent such as water inparticular, and where at least one reaction product is insoluble or oflow solubility in said solvent.

In the case of precipitation, stabilization is eliminated.

The term “coagulation” for the purposes of this specification describesthe aggregation of particles, in other words the at least one partialelimination of colloidal states and/or of states of ultrafinedistribution, such as the settling-out and/or caking especially ofcolloidal, suspended and/or emulsified substances, chemocoagulationthrough acids or alkalis, the precipitation of ampholytes at theisoelectric point, and/or the precipitation of substances by means ofultrasound coagulation. Coagulation is often a component step in thedeposition of precipitation products and very fine particles.

The term “deposition” relates in particular to a downward movement andsedimentation of particles which are already present in the aqueouscomposition. Deposition can be intensified by coagulation of particlesand may also affect colloidal particles, precipitations and/or theformation of a deposit.

The term “salting out” for the purposes of this specification describesthe formation of salt by formation of a usually crystallineprecipitation product and/or deposit.

The term “formulation” encompasses multicomponent mixtures in the formof aqueous compositions which have a specific constitution and as apaint formulation, for example, are tailored for particular properties.

The term “polymer(s)” for the purposes of this specification denotesoligomer(s), polymer(s), and copolymer(s), mixtures thereof, and inparticular as well the compounded forms thereof on an organic and/orlargely organic basis. For the purposes of this specification, the“polymer(s)” is or are typically present wholly or primarily in the formof polymer(s) and/or copolymer(s).

The term “copolymers” for the purposes of this specification describespolymers which are composed of two or more different kinds of monomerunits. In this context it is possible to subdivide copolymers into fiveclasses, as illustrated for a binary copolymer synthesized from twodifferent comonomers A and B:

1. random copolymers, in which the distribution of the two monomers inthe chain, in the backbone and/or in the dendrimer is arbitrary(AABABBBABAABBBABBABAB . . . );

2. gradient copolymers, in principle similar to the random copolymers,but with a varying fraction of a monomer in the profile of the chain,the backbone and/or the dendrimer (AAAAAABAABBAABABBBAABBBBBB);

3. alternating copolymers, with a regular arrangement of the monomersalong the chain, the backbone and/or the dendrimer (ABABABABABABABABABAB. . . );

4. block copolymers, consisting of relatively long sequences or blocksof each monomer (AAAAAAAAABBBBBBBBBBBB . . . ), also referred to, inaccordance with the number of blocks, as diblock, triblock, multiblockcopolymers;

5. graft copolymers, in which blocks of one monomer have been graftedonto the blocks, the chain, the backbone and/or the dendrimer of anothermonomer.

The term “derivatives” for the purposes of this specification denotes aderived substance of similar structure to a corresponding parentsubstance. Derivatives are substances whose molecules, instead of atleast one H atom or at least one functional group, possess at least onedifferent atom or at least one different group of atoms, and/or in whichone or more atoms/groups of atoms have been removed.

The expression “(meth)acryl . . . ” for the purposes of the presentinvention is intended to encompass methacryl . . . , acryl . . . and/ormixtures of both.

The term “compounded particles” identifies particles which are composedof different substances and often have an especially optimizedcomposition.

The term “water-insoluble particles” for the purposes of thisspecification means that the water-solubility of the particles is so lowthat there is no passage of individual constituents of the particles,such as the stabilization attaching to the particle surface, and/orsmall amounts of the substance of the particles, into the aqueous phaseat room temperature, or there is such passage but only up to 10% byweight, preferably up to 5% by weight, up to 2% by weight, or up to 1%by weight, within a day. These water-insoluble particles also include“stabilized particles” where the stabilization is present and/or takesplace in the aqueous phase. The stabilization on the particle surfacemay be established for example with a nonionic and/or ionic emulsifier,with ions, with a flow control agent and/or with a thickener.

The term “long-chain” for the purposes of the present inventionencompasses carbon chains with 4 or more, preferably four to 20, moreparticularly six to 18, carbon atoms.

DETAILED DESCRIPTION

For the purposes of the present invention, in methods for coatingsurfaces of objects which may optionally have been precoated (=surfacesto be coated), the surfaces to be coated are first activated with anactivating agent. Here, with the activating agent on the surfaces to becoated, a rinse-resistant layer (=activating coat) is formed with afirst aqueous composition, preferably with a stable aqueous compositionin the form of a solution and/or dispersion (=suspension and/oremulsion). Here, by means for example of cationic or anionicprecipitation potential, a precipitation reaction, a coagulation, asalting-out of substances present in solution in a solvent, and/or adeposition of particles and/or of colloidal, ultrafine and/or fineparticles, is induced. Then a second, optionally rinse-resistant layer(=secondary coat=precipitation coat) is formed on the surface that isactivated (=coated with activating substance). Since in this case it ispossible for polyvalent ions and/or molecules having two or more anionicor two or more cationic functions (polyfunctional molecules) to have ahigher precipitation potential and to coagulate to a greater extent thanmonovalent anions, than monovalent cations and/or than monofunctionalmolecules, the former are preferred in an activating agent. This appliesto oppositely charged ions and molecules in an electrolyte.

Surprisingly it has been found that even anionic polyelectrolytes canlead to the precipitation of an anionically stabilized dispersion.Surprisingly it has been found that, conversely, cationicpolyelectrolytes as well may lead to the precipitation of a cationicallystabilized dispersion.

The method of the invention may preferably be distinguished by the factthat the ions, complexes and/or compounds of the activating coat maydiffuse into the aqueous composition to form the secondary coat, and/ormay interact and/or react, and/or that the first coat (=activating coat)is at least partly dissolved and/or detached, it not being absolutelynecessary for material of the first coat to be taken up into thesecondary coat.

In the method of the invention, the second aqueous composition to form asecondary coat (=precipitation coat) may preferably comprise at leastone precipitable substance, at least one kind of depositable particleand/or at least one depositable compound.

In individual embodiments of the invention, to form an activating coat,it is possible preferably, additionally, for an auxiliary voltage, moreparticularly of less than 100 V, to be applied, the auxiliary voltagebringing about ion migration, but not initiating precipitation, notinitiating deposition and/or not initiating salting out. This auxiliaryvoltage may accelerate the formation of the activating coat and/or mayimprove coat quality.

In the method of the invention, the at least one precipitable substance,the at least one kind of depositable particles and/or the at least onedepositable compound is able preferably to enter into a precipitationreaction and/or a salting-out reaction with the ions, complexes and/orcompounds of the activating coat, forming a secondary coat ofprecipitated and/or deposited substances on the activating coat.

In one preferred method of the invention, the secondary coat may befilmed and/or crosslinked, the secondary coat may be treated chemicallyand/or thermally, in order to apply and/or fix the substances on thesubstrate, and/or the secondary coat may be further coated.

The objects to be coated may be objects made of any desired material.The objects preferably have surfaces of metal, alloy, plastic, compositematerial, natural material, glass and/or ceramic. Serving as objects mayalso be any metallic objects requiring protection from corrosion. Theobjects may in principle, however, be any objects comprising in eachcase at least one plastic, composite material, natural material, glass,ceramic and/or metallic material, and also combinations thereof, whichoptionally are already coated and/or which now are to be coated. Forexample, plastics elements intended, for example, for vehicle bodies,fenders, appliances, and buildings can be coated in accordance with theinvention. Elements made from metallic materials may also have beenjoined to elements made from other materials, such as plastic, forexample.

As surfaces or substrates it is possible in principle in step I. to usesurfaces of all kinds of materials—optionally also those of two or moredifferent kinds of materials adjacently and/or successively in themethod of the invention. Among the metallic materials, all kinds ofmetallic materials are possible in principle, more particularly those ofaluminum, iron, copper, magnesium, titanium, zinc, tin and/or alloysthereof containing aluminum, iron, steel, copper, magnesium, nickel,titanium, zinc and/or tin. The surfaces of the materials may optionallyalso be and/or have been precoated, with zinc or with an alloycontaining aluminum and/or zinc, for example. The metallic substrate mayoptionally have been joined to a plastics component.

As objects to be coated it is possible in principle to use all kinds ofobjects, more particularly those comprising at least one metallicmaterial and/or those having at least one metallic coating.

Particularly preferred objects are, in particular, strips (coils),sheets and panels, parts such as small parts, for example, joinedcomponents, components of complex shape, profiles, rods and/or wiresmade of metal and/or alloy.

In various embodiments the substrates have been precoated—for example,with at least one coating of at least one metallic,nonmetallic-inorganic or organic coating, as for example a hot-dipgalvanizing, zinc-alloying or aluminum-alloying coat, with at least onepretreatment coat based, for example, on phosphate,silane/silanol/siloxane, titanium compound and/or zirconium compound,with at least one electrolytically applied coating, such as an anodizingcoat, for example, with at least one subsequently applied coat forsealing and/or modifying the coating present beneath it, with at leastone organic coating, such as a primer coat and/or a paint coat, forexample. On organic substrates as well, for example, it is possible forexample to apply at least one coating, such as an antistatic coat,metallic coat, paint coat and/or sealing coat, for example.

In the case of a prior pretreatment before activation of a surface withan activating agent, the surfaces to be treated may if required be firstsubjected to alkaline cleaning, acid pickling and/or water rinsing, andmay optionally be contacted with a composition for pretreatment, thelatter more particularly for the purpose of forming a conversion coat.The surfaces thus treated and/or coated may then be coated optionallywith a primer and/or with an optionally formable protective coat, moreparticularly with an anticorrosion primer, and/or may optionally beoiled. Oiling is used in particular for temporary protection of thetreated and/or coated surfaces, especially metallic surfaces, when, forexample, these surfaces are to undergo temporary storage.

Any kind of pretreatment is possible in principle: for example it ispossible to use aqueous pretreatment compositions based on phosphate,phosphonate, silane/silanol/siloxane, polysiloxane, lanthanide compound,titanium compound, hafnium compound, zirconium compound, zinc particles,acids such as vinylphosphonic acids, metal salt, waterglass and/ororganic polymer.

In many embodiments it is necessary first to clean the surfaces ofmetallic substrates and/or of metallic coatings, by means for example ofan alkaline cleaning such as degreasing, for example, and/or by means ofacid pickling, with a subsequent rinse with water. If a metallicsubstrate is freshly manufactured and/or if a metallic coating isfreshly applied, there is generally no need for cleaning. On the otherhand it is advisable in numerous embodiments, including other kinds ofsurfaces, such as those of plastics, for example, to carry out cleaning,to remove dirt and dust, for example, and optionally to carry outantistatic treatment.

The activation serves to prepare the substrates that are to be coatedwith a secondary coat, and the at least one activating substance in theactivating coat, or in the activating coat which remains after rinsing,contributes to the precipitation, salting-out and/or deposition ofparticles, thereby forming a secondary coat. In numerous embodiments itis desired for the secondary coat to have a very high dry film thicknessand to be formed as far as possible in one process step.

With the method of the invention at least one activating coat is formedwith the aqueous activating agent that comprises at least one activatingsubstance. The activating coat is preferably rinse-resistant.

Each activating coat can be formed in particular with an aqueousactivating agent based on cationic and/or anionic polyelectrolytesand/or on cationic or anionic salts.

The activating agent and/or the activating coat formed from itcomprises/comprise as activating substance(s) at least onepolyelectrolyte, at least one chemically modified polyelectrolyte, atleast one inorganic salt, at least one organic salt, at least onecomplexing agent, at least one complex, at least one acid and/or atleast one base, these constituents not adversely affecting one another.The at least one activating substance acts preferably as a precipitatingagent, as a salting-out agent and/or as an agent for deposition.

The polyelectrolytes here are preferably water-soluble anionic orcationic compounds with usually a high chain length. More particularlythey are an organic polymer and/or copolymer which has a chain, abackbone and/or a dendrimer. In many embodiments they are branchedand/or linear polymers and/or branched and/or linear copolymers. Thepolyelectrolytes often have molecular weights in the range from 200g/mol to 20 million g/mol, preferably in the range from 500 g/mol to 12million g/mol, from 2000 g/mol to 8 million g/mol, or from 12 000 g/molto 5 million g/mol, more preferably in the range from 50 000 g/mol to 3million g/mol or from 200 000 g/mol to 2 million g/mol. In certainembodiments the polyelectrolytes may have molecular weights in the rangefrom 1000 to 800 000 g/mol, from 8000 to 300 000 g/mol, or from 30 000to 150 000 g/mol. In certain other embodiments the polyelectrolytes mayhave molecular weights in the range from 12 000 to 16 000 000 g/mol,from 28 000 to 14 000 000 g/mol, from 80 000 to 9 500 000 g/mol, or from120 000 to 7 000 000 g/mol.

In this context it may be useful in the case of highly water-solublepolyelectrolytes to take measures to improve the rinse resistance, bychemical modification of the polyelectrolyte, by the addition of afixing aid such as an adhesion promoter and/or thickener, for example,with an intermediate drying procedure, and/or with crosslinking of thepolyelectrolyte, for example. Particular preference is given tointermediate drying prior to rinsing, especially when the cationicpolyelectrolytes have not been chemically modified and when no othermeasures are taken to raise the rinse-resistance.

If the polyelectrolyte used is a chitosan or a chitosan modifiedchemically with silane/silanol/siloane, for example, it is preferred forthe pH of the aqueous composition to be in the range from 1.5 to 12,preferably from 2 to 7 or from 3 to 6, for its concentration to be inthe range from 0.001% to 2% by weight, preferably in the range from0.01% to 1.5% by weight or from 0.05% to 1% by weight, and/or for themolecular weight of the chitosan to be in the range from 161 g/mol to 4000 000 g/mol, preferably in the range from 5000 g/mol to 3 000 000g/mol, or from 150 000 g/mol to 2 000 000 g/mol.

In particular, at least one polyelectrolyte and/or at least oneconstituent of a polyelectrolyte may have been chemically modified, withattachment groups, for example, from a reaction, for example, of apolyelectrolyte and/or the precursor of a polyelectrolyte with anadhesion promoter and/or with adhesion-promoting groups, through uptakeof chemical groups and/or through polymerization incorporation and/orcopolymerization, for example.

Polyelectrolytes with attachment groups have proven particularlyappropriate, in particular, as polyelectrolyte modifications.

As attachment groups which impart adhesion in the case of an anionic orcationic polyelectrolyte, it is possible to use chemical groups selectedfrom the group consisting of chemical groups of polyfunctional epoxides,isocyanates, primary amines, secondary amines, tertiary amines,quaternary amines, amides, imides, imidazoles, formamides, Michaelreaction products, carbodiimides, carbenes, cyclic carbenes,cyclocarbonates, polyfunctional carboxylic acids, amino acids, nucleicacids, methacrylamides, polyacrylic acids, polyacrylic acid derivatives,polyvinyl alcohols, polyphenols, polyols having at least one alkyland/or aryl radical, caprolactam, phosphoric acids, phosphoric esters,epoxide esters, sulfonic aids, sulfonic esters, vinylsulfonic acids,vinylphosphonic acids, catechol, silanes and also the silanols and/orsiloxanes formed therefrom, such as those, for example, based on alkoxysilanes, amino silanes, epoxy silanes, and vinyl silanes, triazines,thiazoles, thiazines, dithiazines, acetals, hemiacetals, quinones,saturated fatty acids, unsaturated fatty acids, alkyds, esters,polyesters, ethers, glycols, cyclic ethers, crown ethers, anhydrides,polysaccharides selected from pectins, alginates, glycogens, amyloses,amylopectins, calloses, celluloses, and hemicelluloses, and also ofacetylacetones and of beta-diketo groups, carbonyl groups, and hydroxylgroups. In this context it should be borne in mind that although thefunctional groups (e.g. alcohols) are identical among differentattachment groups from those specified, the tertiary structure meansthat differences in adhesion may occur.

In principle it is possible for the attachment groups to be bonded or tohave been bonded covalently, via addition and/or substitution reactions,with customary reactions that are known to the skilled person, such as,for example, via in each case at least one esterification reaction, acoupling, a double bond and/or an alcohol, to a polyelectrolyte.Particularly suitable silanes, including the corresponding silanolsand/or siloxanes that are formed therefrom(=silanes/silanols/siloxanes), are alkoxy silanes having at least oneepoxy group, having at least one isocyanato group and/or having at leastone double bond with radical effect. To form an activating coat it ispreferred to use at least one modified polyelectrolyte which has beenmodified with a silane/silanol/siloxane having a degree of condensationin the range from 1 to 30 or from 1 to 20 monomer units per molecule.Generally speaking, these silicon compounds here may be or may have beencoupled onto the chain, the backbone and/or the dendrimer of thepolyelectrolyte via in each case at least one amino group, carboxylgroup, isocyanato group, epoxy group, hydroxyl group and/or via at leastone double bond, for example.

Having been found especially appropriate as derivatives ofpolyelectrolytes are polyelectrolytes with silane/silanol/siloxane,polysiloxane, carboxylate, hydroxyl, phosphate, phosphonate, sulfonate,urea, urethane and/or aromatic groups, and also the oligomers, polymersand copolymers thereof with medium-length and/or long-chain (=havingmore than 4 C atoms) hydrophobic polymers modified polyelectrolytes suchas, for example, polyethyleneimines modified in such a way. Thederivatives as well may diversely be copolymers such as, for example, inparticular by addition during the polymerization of coupling groupsknown to the skilled person, especially aziridines,with—especially—polyfunctional epoxides, alcohols, amides, esters,isocyanates, imines, carboxylic acids, thiols, acrylates, methacrylates,vinyls, and substances having reactive double bonds and/or triple bonds.

Surprisingly it has been found that individual polyelectrolytes, in thecase of certain combinations of an aqueous cationic or anioniccomposition to form a secondary coat, may be both cationic and anionicin the character of their effect, depending on the stabilization of theaforementioned aqueous composition. In other words, with the same salts,it is possible in principle for the cationic moiety in one instance andthe anionic moiety in one instance to exert an effect on the secondarycoating.

If the aqueous composition to form the secondary coat is cationicallystabilized, the anionic moiety of the salt brings about, for example,the precipitation. If the aqueous composition to form the secondary coatis anionically stabilized, the cationic moiety of the salt brings about,for example, the precipitation.

In this case it is the nature of the stabilization that decides whether,for example, the precipitating effect of the salt is anionic or cationicand whether anionic or cationic salts are present. The reason is that inthis case, emulsifiers that are likewise present decide on the anionicor cationic effect, and/or ionic groups that are likewise present, suchas carboxylates, for example, decide on the anionic effect, or, forexample, quaternary ammonium compounds decide on the cationic effect.The emulsifiers are part or even a major constituent in thestabilization of the particles and/or of the dispersions, which mayeither be anionic or cationic. Ionic stabilization comes either fromionic groups which are incorporated directly into the polymer, and/orfrom ionic emulsifiers. The emulsifiers have a hydrophilic moiety thathas either a cationic nature or an anionic nature and thereforedetermines whether the particles they stabilize and/or the dispersionthey stabilize has an anionic or cationic character.

Salts which can be used with preference are as follows: borides,borates, carbides, carbonates, hydrogen carbonates, chromates,dichromates, halides such as, for example, fluorides, chlorides,bromides, bromates and/or iodides, iodates, chlorates, hydroxides,permanganates, molybdates, niobates, oxides, hydroxides, nitrides,nitrates, nitrites, phosphides, phosphates such as, for example,aminoethyl dihydrogen phosphates, orthophosphates, hydrogen phosphates,dihydrogen phosphates, glycerol phosphates, and hexahalo phosphates,phosphonates, silicides, silicates, sulfites, hydrogen sulfites,sulfates, hydrogen sulfates, thiosulfates, sulfides, hydrogen sulfides,dithionates, peroxodisulfates, tantalates, titanates, tungstates,zincates, zirconates, azides, aluminates, ferrates, stannates and/orderivatives thereof, persalts, salts having two or more anionicconstituents or having two or more cationic constituents, amides, saltswith at least one alkyl group, saturated fatty acid salts having alinear alkyl chain with 3 to 29 C atoms in the chain, monounsaturatedfatty acid salts having a linear alkyl chain with 10 to 23 C atoms inthe chain, polyunsaturated fatty acid salts having a linear alkyl chainwith 17 to 21 C atoms in the chain, saturated fatty acid salts with abranched alkyl chain having 3 to 19 C atoms in the chain, and/orderivatives thereof, and also, in particular, acetates, acetonates,acetylacetonates, benzoates, butyrates, isobutyrates, carbamates,caproates, cinnamates, citrates, cyanides, cyanates, thiocyanates,formates, fumarates, glutarates, lactates, malates, malonates, alkylmalonates, oxalates, propionates, pyruvates, gluconates, laurates,linoleates, maleates, myristates, oleates, palmitates, picrates,saccharates, salicylates, stearates, succinates, tartrates, thionates,valerates and/or derivatives thereof.

Particularly preferred anionic or cationic salts are acetates, amides,cyanates, thiocyanates, cyanides, butyrates, cinnamates, citrates,formates, fumarates, glutarates, isobutyrates, lactates, malates,malonates, oxalates, propionates, and/or pyruvates of polyvalentcations. Especially preferred are acetates and formates of polyvalentcations such as, for example, calcium acetate, calcium formate, aluminumacetate, and aluminum formate.

Preferred salts that are commonly both anionic and cationic are thoselisted below, with the nature of the stabilization determining theiranionic or cationic effect:

aluminum acetate, aluminum acetylacetonate, aluminum benzoates, aluminumboride, aluminum diethylmalonate, aluminum fluoride, aluminumfluorosilicates, aluminum hydroxide, aluminum oxalate, aluminum oxide,aluminum phosphate, aluminum salicylate, aluminum silicate, aluminumsulfate, aluminum ammonium sulfate hydrate, aluminum pentaborate,aluminum peroxyborate, aluminum tetra borate,ammonium sulfate, ammonium borate, ammonium calcium phosphate, ammoniumcarbamate, ammonium hydrogen carbonate, ammonium chloride, ammoniumchlorostannate, ammonium chromate, ammonium peroxychromate, ammoniumbromium sulfate, ammonium copper chloride, ammonium fluoroborate,ammonium fluorosilicate, ammonium iodate, ammonium iron sulfate,ammonium magnesium chloride, ammonium magnesium phosphate, ammoniummagnesium sulfate, ammonium permanganate, ammonium manganese phosphate,ammonium molybdate, ammonium myristate, ammonium oxalate, ammoniumoxaloferrate, ammonium palmitate, ammonium periodate, ammoniumphosphate, ammonium phosphomolybdate, ammonium phosphotungstate,ammonium picrate, ammonium rare earth sulfate, ammonium saccharate,ammonium sulfite, ammonium tartrate, ammonium thionate, ammoniumvanadate,calcium acetate, calcium hydrate, calcium aluminate, calcium benzoates,calcium metaborate, calcium boride, calcium carbonate, calcium chloridealuminate, calcium chloride fluoride phosphate, calcium chromate,calcium chromide, calcium cinnamate, calcium citrate, calcium ferrite,calcium fluorosilicate, calcium fluoride, calcium formate, calciumfumarate, calcium gluconate, calcium glycerophosphate, calciumhydroxide, calcium iodate, calcium isobutyrate, calcium lactate, calciumlaurate, calcium linoleate, calcium magnesium carbonate, calciummagnesium silicate, calcium malate, calcium maleate, calcium malonate,calcium butyrate, calcium molybdate, calcium oleate, calcium oxalate,calcium oxide, calcium palmitate, calcium phenoxide, calcium phosphate,calcium phosphite, calcium quinate, calcium silicate, calciumsalicylate, calcium silicide, calcium stearate, calcium succinate,calcium sulfate, calcium tartrate, calcium thionate, calcium tungstate,calcium valerate, iron acetylacetonate, iron boride, iron carbide, ironcarbonate, iron carbonyl, iron chromide, iron citrate, iron fluoride,iron iodate, iron lactate, iron nitride, iron nitrosocarbonyl, ironoxalate, iron oleate, iron oxide, iron phosphate, iron phosphide, ironphosphite, iron silicate, iron silicide, iron sulfate, iron sulfide,iron tartrate,magnesium antimonide, magnesium benzoate, magnesium borate, magnesiumbromate, magnesium carbonate, magnesium chromide, magnesium citrate,magnesium fluoride, magnesium formate, magnesium hydroxide, magnesiumiodate, magnesium lactate, magnesium laurate, magnesium molybdate,magnesium myristate, magnesium oleate, magnesium oxalate, magnesiumoxide, magnesium palmitate, magnesium phosphate, magnesium silicate,magnesium silicide, magnesium stearate, magnesium sulfate, magnesiumsulfide, magnesium tartrate,manganese benzoate, manganese carbonate, manganese chromide, manganesecitrate, manganese fluoride, manganese glycerophosphate, manganesehydroxide, manganese lactate, manganese oxalate, manganese oxide,manganese phosphate, manganese silicate, manganese silicide, manganesesulfide, manganese tartrate,molybdenum bromide, molybdenum carbide, molybdenum carbonyl, molybdenumchloride, molybdenum hydrotetrachlorohydroxide, molybdenum hydroxide,molybdenum iodide, molybdenum oxide, molybdenum phosphate, molybdenumsulfide,titanium carbide, titanium nitride, titanium oxide, titanium phosphide,titanium sulfate, titanium sulfide,tungsten boride, tungsten bromide, tungsten carbide, tungsten carbonyl,tungsten iodide, tungsten oxide, tungsten phosphide, tungsten silicide,tungsten sulfide,zinc acetate, zinc aluminate, zinc benzoate, zinc butyrate, zinccaproate, zinc carbonate, zinc chromate, zinc citrate, zinc fluoride,zinc formate, zinc hydroxide, zinc iodate, zinc lactate, zinc laurate,zinc permanganate, zinc oleate, zinc oxalate, zinc oxide, zincphosphate, zinc salicylate, zinc silicate, zinc sulfide, zinc tartrate,zinc tellurate, zinc valerate,zirconium bromide, zirconium carbide, zirconium carbonate, zirconiumfluoride, zirconium nitride, zirconium oxide, zirconium phosphide,zirconium silicate and/or derivatives thereof.

For anionic and for cationic salts it is the case that preferably instep III. the activating coat is formed with at least one activatingsubstance selected from the group consisting of melamine salts, nitrososalts, oxonium salts, ammonium salts, salts with quaternary nitrogencations, salts of ammonium derivatives, and metal salts which in thecase of cationic salts have at least one polyvalent element as cationiccomponent and which in the case of anionic salts have at least onemonovalent element as cationic component. With particular preferencehere the activating coat is formed of at least one activating substanceselected in the case of cationic salts from the group consisting ofmetal salts of Al, B, Ca, Fe, Mg, Mn, Mo, Ti, W, Mn, Zn, and Zr, andselected in the case of preferably anionic salts from the groupconsisting of metal salts of Li, Na, and K.

The activating agents comprising anionic or cationic polyelectrolyteand/or anionic or cationic salt may adopt very different pH values,preferably those in the range from 3 to 12, more particularly pH valuesin the range from 4 to 11 or 6 to 10. The employable pH value of theactivating substances is in some cases very substance-specific and isknown in principle.

The aqueous composition (=activating agent) to form the activating coatpreferably has a pH in the range from 2 to 12, from 3 to 11, or from 3.5to 10, it often being advantageous not to carry out partial pickling andpartial dissolution of the substrate surface, or not to do so to asubstantial extent (low or high pH values pickle and produce activatedmetallic surfaces of good reactivity). Particularly if the activatingagent comprises at least one anionic polyelectrolyte, its pH value ispreferably in the range from 3 to 12 or 5 to 10, more preferably 6 to 9.Particularly if it comprises at least one cationic polyelectrolyte, itspH value is preferably in the range from 3 to 9 or 4 to 8, morepreferably 5 to 7. Particularly if it comprises at least one anionicsalt or at least one cationic salt, its pH is preferably in the rangefrom 3 to 8 or 5 to 12, more preferably in the range from 4 to 11 or 5to 10. The composition with which an activating agent is appliedpreferably has a pH value in the range from 4 to 7.

For the selection of the pH value and of the concentration of thecomposition of the activating agent, it is preferred for it to be astable solution, a stable dispersion and/or for the polyelectrolytestill to be in the form of polycations, and not only in the form ofuncharged molecules, at the pH value selected and at its concentration.

Furthermore, as and when required, the activating agents, as well aswater and activating substances, may comprise further substances suchas, for example, alcohols and/or thickeners such as, for example,cellulose, polysaccharides, welan gum, xanthan gum and/or polysiloxanes,preferably in a total amount in the range from 0.05 to 10 g/L or from0.3 to 6 g/L. Furthermore, the activating agent and/or the activatingcoat may also comprise other substances such as, for example, fillers,mixtures such as compounded mixtures, and auxiliaries such as, forexample, coat-forming substances such as phyllosilicates, agents formodifying the pH value, adhesion promoters such as, for example,silanes, wetting agents such as, for example, surfactants, stabilizers,thixotropic agents, thickeners, wetting agents, defoamers,preservatives, biocides and/or agents for adapting the pH to lowerand/or higher values. The activating agent and/or the activating coatmay preferably further comprise, in some embodiments, in each case atleast one organic polymer, at least one amine, at least one kind oforganic and/or inorganic particles and/or at least one dye.

The substances of the activating agent and/or of the activating coat,especially the polyelectrolytes, are preferably largely water-soluble orcompletely water-soluble. Or at least some of the various substances inthe activating agent and/or the activating coat are water-soluble. Inthat case it may be difficult to produce a rinse-resistant activatingcoat. Particularly the water-solubility, but also the hygroscopicbehavior and/or corrosion-promoting behavior of electrically conductiveaqueous electrolyte solutions have contributed to a situation in which,in the industrial corrosion control sector, polyelectrolytes are rarelyused as major constituents of an anticorrosion coating.

The activating agent preferably includes an amount of at least oneactivating substance such as polyelectrolyte and/or salt in the rangefrom 90% to 100% by weight or from 95% to 99% by weight of the solidsand active ingredients.

The amount of at least one activating substance in the first aqueouscomposition (=activating agent) is frequently in the range from 0.01 to500 g/L. This amount is preferably in the range from 1 to 400 g/L, from3 to 300 g/L, from 5 to 240 g/L, from 8 to 180 g/L, from 12 to 150 g/L,from 18 to 120 g/L, from 24 to 96 g/L, or from 30 to 70 g/L. In certainembodiments this amount is in the range from 0.5 to 200 g/L, from 0.8 to150 g/L, from 1.2 to 120 g/L, from 2 to 90 g/L, from 4 to 80 g/L, from 5to 70 g/L, from 6 to 60 g/L, from 8 to 50 g/L, from 10 to 40 g/L, orfrom 20 to 30 g/L. The amount of at least one activating substance andof the other solids and active ingredients present in the first aqueouscomposition is frequently in the range from 0.01 to 500 g/L. Preferablythis amount is in the range from 1 to 420 g/L, from 3 to 320 g/L, from 5to 260 g/L, from 8 to 210 g/L, from 12 to 170 g/L, from 18 to 140 g/L,from 24 to 110 g/L, from 30 to 90 g/L, or from 40 to 65 g/L. Theactivating agent preferably includes an amount of polyelectrolytesand/or of ionic salts in the range from 90% to 100% by weight or from95% to 99% by weight of the solids and active ingredients.

The activating agent preferably contains at least one anionic orcationic polyelectrolyte in the range from 0.02 to 400 g/L, from 1 to250 g/L, from 10 to 180 g/L, from 30 to 140 g/L, or from 50 to 110 g/L,but in certain embodiments in the range from 0.5 to 60 g/L, from 2 to 40g/L, or from 6 to 25 g/L.

The activating agent preferably includes an amount of at least oneanionic or cationic salt in the range from 5 to 500 g/L, more preferablyin the range from 10 to 360 g/L, from 25 to 280 g/L, from 40 to 230 g/L,from 60 to 180 g/L, or from 85 to 140 g/L, but in certain embodiments anamount in the range from 15 to 130 g/L, from 30 to 100 g/L, or from 45to 65 g/L.

With regard to the salts it is important to ensure a sufficiently highamount in order to allow the formation of an activating coat and notmerely of an inefficient, excessively thin coat or virtually no coat.The reason is that in the aqueous solution the salts must frequentlyattain their saturation concentration in order to form an activatingcoat.

If the total amount of activating substances in the activating agent islower than 0.01 g/L, the activating coat deposited is typically tooinsubstantial. If the total amount of substances or of activatingsubstances in the activating agent is greater than 500 g/L, the solutiontypically becomes too viscous to allow homogeneous coating of theworkpiece.

Overall, when applying the activation, in certain embodiments for OEMmanufacture, it should be ensured that not only the pH value of the bathsolution of the activating agent, but also the amount of solids andactive ingredients of the activating substances, is kept constant withinnarrow ranges in the method of the invention, such as ±0.5 points interms of pH value and/or ±20% or ±10% in terms of amount of solids andactive ingredients. If the above-described limits are observed whenapplying the activation, it is possible for particularly uniform andreproducible coat formation to take place. Moreover, it is preferred toensure that fractions of cleaner solution are not entrained into theactivating tank.

Coating with an activating coat may take place preferably attemperatures between 5 and 95° C., more preferably at room temperature,or at temperatures between 15 and 50° C. In this case, in a number ofembodiments, the substrate may have a temperature in the range from 10to 180° C. and more particularly in the range from 40 to 120° C. or from60 to 90° C.

The activating coat may be applied for example by rolling, flow coating,knife coating, injecting, spraying, brushing and/or dipping, including,for example, dipping at elevated temperature of the aqueous compositionand/or of the substrate, and optionally by subsequent squeeze-off with aroller, for example. For this contacting and coating as well, particularpreference is given to application by a dipping process.

For certain industrial procedures and systems it is particularlyadvantageous if at least one rinse-resistant activating coat is formedon the substrate. The rinse-resistant activating coat may also be formedof at least two activating coats applied in succession, optionally withintermediate drying after the application of the first activating coat,and these activating coats and their activating agents optionally havedifferent chemical compositions.

On rinsing of the substrates coated with activating agent, theactivating coat often is to be removed very little, and must not beremoved completely. It is therefore advantageous if the activating coatis sufficiently rinse-resistant for the systems and procedures used.When the activating coat is being rinsed, it is necessary for it not tofully dissolve and/or become detached in the course of rinsing. It istherefore desired for the activating coat to be sufficientlyrinse-resistant to still have a residual coat thickness after rinsing(=remaining activating coat).

In this context it is particularly preferred to apply an extremelyrinse-resistant activating coat. The rinse resistance is favorablyinfluenced for example by the intermediate drying step after activation,by the chemical modification of the polyelectrolytes, by the selectionof polyvalent salts/ions/compounds, and/or by the selection of salts oflow solubility. Alternatively the rinse resistance of the activatingcoat can also be significantly increased by carrying out intermediatedrying of the activating coat prior to rinsing. This intermediate dryingmay be a slight partial drying or a substantial or complete drying.

Alternatively it may be advisable for the activating coat prior torinsing to be heated, to undergo at least partial chemical modification,by salt replacement, such as, for example, by formation of and/or fixingof a salt of lower water-solubility, particularly on the surface of theactivating coat. Furthermore, for rinsing, the activating coat may havea different temperature and/or a different pH value from the rinsingliquid. Every variant and every arbitrary combination of all of thesemeasures may help to reduce or even to avoid the depletion of theactivating agent, which in particular has good water-solubility, fromthe activating coat.

One way of improving the rinse resistance of the activating coat maytake place with adhesion promoters and/or with adhesion-promotingchemical groups. A second possibility is the use of an electricauxiliary voltage when applying an activating coat, of less than 100 Vor of less than 60 V or of less than 30 V or than 5 V, for example, withany electrical voltage that may be used being employed only as aninitial auxiliary voltage, but initiating precipitation. It isparticularly preferred in this context to apply an auxiliary voltage ofless than 2.5 V, of less than 1 or of less than 0.5 V, more particularlyin the form of direct voltage, with preferably virtually no currentflowing. In the case of a current flow, the current strength is lessthan 0.1 A/dm² or, preferably, less than 0.01 A/dm². In this case theauxiliary voltage may initiate, for example, the migration of ions, butnot precipitation, deposition and/or salting out. This auxiliary voltagemay accelerate and/or improve the formation of the coat. In the majorityof embodiments, however, no electrical voltage is applied from outside.If a dip coating is to be applied, it is possible to operateelectrolessly or, optionally, only with an electrical auxiliary voltage,but the electrical auxiliary voltage, in contrast to the situation withan electrocoat material, is not used for precipitating, depositing orsalting-out an aqueous composition. An electrical auxiliary voltageapparently has the effect of particle migration and hence of an increasein concentration on the part, for example, of the substance to beprecipitated and/or on the part of the particles to be coagulated, butit does not bring about any separation of water from substances presenttherein, owing to the electrical field and current, as in the case of anelectrocoating operation.

Furthermore, a rinsing liquid may also comprise a fixing aid for fixingand/or modifying the activating agent, by means of a salt exchange, forexample.

Since often in the case of a rinsing operation a part of the freshcoating is rinsed away, it is advantageous to verify the remainingamounts of the activating coat, in terms of chemical elements, forexample, by means of X-ray fluorescence analysis (XFA), especiallybefore applying a secondary coating. Here, the lower detection limit forthe elements silicon, titanium, zirconium, or manganese, in the order ofmagnitude of 1 mg/m², indicates the lower limit. When using standardizedprocess conditions as in the examples, therefore, the rinse resistanceof the activating coat may also be evaluated from the measurement valuesfrom XFA.

In one preferred method of the invention, it is possible in step III.for the activating coat to be formed with at least one activatingsubstance selected from cationic polyelectrolytes from the groupconsisting of polyphenols, polyallylamines, including thepolydiallylamines and polytriallylamines, polyethyleneimines, includingthe polydiethyleneimines and polytriethyleneimines, polyvinylamines,including the polydivinylamines and polytrivinylamines,polyvinylpyridines, chitosans, derivatives thereof, modificationsthereof with at least one attachment group and/or with at least onesilane/silanol/siloxane, copolymers thereof, and mixtures thereof.

Examples of specific compounds include the following:polydiallyldimethylammonium chloride, polyvinylammonium chloride,polyethyleneimineammonium chloride. Polyelectrolytes modified withattachment groups may in particular be considered to be derivatives ofthese polyelectrolytes.

In one preferred method of the invention, the activating coat may beformed with an activating agent comprising an aqueous composition whichcomprises at least one permanently cationic and/or latently cationicorganic polymer and/or copolymer which is in solution in water and whichhas a chain, a backbone and/or a dendrimer based on polyethyleneimine,polyvinylamine and/or chitosan, and/or derivatives thereof and/ormodifications thereof, forming an activating coat which comprises atleast one permanently cationic and/or latently cationic polymer and/orcopolymer.

In one preferred method of the invention, the activating coat may beformed of an activating agent comprising polymers, copolymers of atleast two polymers and/or copolymers selected from those ofpolyethyleneimines, polyvinylamines, chitosans, and of derivatives ofthese polymers and copolymers thereof, and mixtures thereof.

In one preferred method of the invention, the activating coat may beformed of an activating agent comprising polyethyleneimine,polyethyleneimine modified with silane/silanol/siloxane, polyvinylamine,polyvinylamine modified with silane/silanol/siloxane, chitosan, chitosanmodified with silane/silanol/siloxane, and mixtures and/or copolymersthereof.

Particularly preferred activating substances in a cationic activatingagent are polyethyleneimines, polyvinylamines, polyallylamines,chitosans and derivatives thereof, melamine salts, nitroso salts,oxonium salts, ammonium salts, salts with quaternary nitrogen cations,salts of ammonium derivatives, and also metal salts which as a cationiccomponent have a polyvalent element and preferably an element selectedfrom the group of Al, B, Ca, Fe, Mg, Mn, Mo, Ti, W, Zn, and Zr.

Particularly preferred here are cations and salts having relativelyhigh, or very high, oxidation states, more particularly M²⁺, M³⁺, M⁴⁺,M⁵⁺ and/or M⁶⁺, where M denotes the cationic fractions, since they bringabout a greater precipitation and/or coagulation effect as the valenceincreases. Such precipitation reactions are also known to the skilledperson from the wastewater treatment sector, for the precipitation oforganic fractions from dispersions. It should, however, be ensured thatthe amount of substances in the aqueous composition to form thesecondary coat, i.e., more particularly, the amount of substances whichcan be precipitated, salted out and/or deposited, is not kept very low,in order to allow precipitation, coagulation, salting out and/ordeposition to be accomplished. The lower limit on amount forprecipitation, coagulation, salting out and/or deposition is dependent,however, on the substance.

The cationic salts include, for example, melamine salts, nitroso salts,oxonium salts, ammonium salts, salts with quaternary nitrogen cations,salts of ammonium derivatives, and also metal salts which as a cationiccomponent have at least one polyvalent element and preferably at leastone element selected from the group of Al, B, Ca, Fe, Mg, Mn, Mo, Ti, W,Zn, and Zr, the anionic counterions of the cationic salts beingpreferably boride, borate, carbide, carbonate, hydrogencarbonate,chromate, dichromate, halide such as, for example, fluoride, chloride,bromide, bromate and/or iodide, iodate, chlorate, hydroxide,permanganate, molybdate, niobate, oxide, hydroxide, nitride, nitrate,nitrite, phosphide, phosphate—such as, for example, aminoethyldihydrogenphosphate, orthophosphate, hydrogen phosphate, dihydrogen phosphate,glycerophosphates, and hexahalophosphate, phosphonate, silicide,silicate, hydrogen sulfite, sulfite, hydrogen sulfate, sulfate,thiosulfate, sulfide, hydrogen sulfide, dithionate, peroxodisulfate,tantalate, titanate, tungstate, zincate, zirconate, azide, aluminate,ferrate and/or stannate groups and/or organic anions.

Other preferred anionic salts are monovalent metal salts and ammoniumsalts, more particular organic salts, very preferably acetates andformates of ammonium, lithium, potassium and/or sodium.

Particularly preferred activating substances in an anionic activatingagent are organic polymer and/or copolymer which a chain, backboneand/or a dendrimer based on polysaccharides such as, in particular,based on alginates and/or pectins, based on polyacrylic acids,polycarboxylic acids, polyvinylphosphonic acids and/or based on polymersthat have been modified, copolymers that have been modified and/orderivatives thereof, the modification being with organic acid radicalssuch as, in particular, carboxylic acid groups, phosphoric acid groupsand/or phosphonic acid groups, and, on the other hand, salts ofammonium, Li, Na and/or K, more particularly based on carbonates,acetates, benzoates, cyanates, butyrates, cinnamates, citrates,formates, fumarates, glutarates, isobutyrates, lactates, malates,malonates, oxalates, propionates and/or tartrates.

Polyphosphoric acids as well are potent precipitating agents.

Anionic salts used may be, in particular, inorganic or organic salts ofammonium, Li, Na and/or K. The anions and anionic salts include, forexample, borides, borates, carbides, carbonates, hydrogen carbonates,chromates, dichromates, halides such as, for example, fluorides,chlorides, bromides and/or iodides, hydroxides, permanganates,molybdates, niobates, oxides, hydroxides, nitrides, nitrates, nitrites,phosphides, phosphates such as, for example, orthophosphates, hydrogenphosphates, dihydrogen phosphates, aminoethyldihydrogen phosphates, andhexachlorophosphates, phosphonates, silicides, silicates, hydrogensulfites, sulfites, hydrogen sulfates, sulfates, thiosulfates, sulfides,hydrogen sulfides, dithionates, peroxodisulfates, tantalates, titanates,tungstates, zincates, zirconates, acetates, amides, benzoates,butyrates, cinnamates, citrates, cyanides, cyanates, thiocyanates,formates, fumarates, glutarates, isobutyrates, lactates, malates,malonates, oxalates, propionates, pyruvates, tartrates especially ofammonium, Li, Na and/or K.

Particularly preferred here are anions of relatively high or very highoxidation states which produce greater precipitation and/or coagulation,especially X²⁻, X³⁻, X⁴⁻, X⁵⁻ and/or X⁶⁻, where X denotes the anionicfractions.

In one preferred method of the invention it is possible in step III. forthe activating coat with an activating agent selected from the anionicpolyelectrolytes of the group specified below.

In one preferred method of the invention it is possible in step III. forthe activating coat to be formed with a first aqueous composition in theform of a solution (=including a colloidal solution), emulsion and/orsuspension which at least one permanently anionic and/or latentlyanionic organic polymer and/or copolymer, in solution in water, that hasa chain, a backbone and/or a dendrimer based on acrylamide copolymers,alginates, pectins, polyacrylic acids, polyvinylsulfuric acids,polyvinylsulfonic acids, polycarboxylic acids, polyphosphoric acids,polysaccharides, polystyrenesulfonates, polyvinylphosphonic acids,polyvinyldialkylpropionates, chemical modifications thereof, derivativesthereof and/or copolymers thereof and optionally also based on organicsalts such as acetates, benzoates, cyanates, butyrates, cinnamates,citrates, formates, fumarates, glutarates, isobutyrates, lactates,malates, malonates, oxalates, propionates and/or tartrates and/orderivatives thereof, a first coat being formed that comprises at leastone permanently anionic and/or latently anionic polymer and/or copolymerand also, optionally, at least one organic salt and/or derivativethereof. In the case of anionic polyelectrolytes as well it may beuseful to perform intermediate drying prior to rinsing, especially ifthe cationic polyelectrolytes are not modified and if no other measuresare taken to make the activating coat rinse-resistant.

Particularly preferred activating substances, as an ionically activatingsubstances in the activating agent, are organic polymer and/or copolymerwhich a chain and/or backbone and/or dendrimers based on polysaccharidessuch as, in particular, based on alginates and/or pectins, polyacrylicacids, polycarboxylic acids, polyvinylphosphonic acids havingacid-functional groups such as, in particular, carboxylic acid groups,phosphoric acid groups and/or phosphonic acid groups, modified polymers,modified copolymers and/or derivatives thereof, carbonates, acetates,benzoates, cyanates, butyrates, cinnamates, citrates, formates,fumarates, glutarates, isobutyrates, lactates, malates, malonates,oxalates, propionates and/or tartrates of ammonium, Li, Na and/or K.

An intermediate drying of an activating coat, especially a freshlyapplied activating coat, prior to rinsing is an opportunity to make anactivating coat more resistant to rinsing. This kind of immobilizing maylead to a situation in which, in the context of a standardized rinsing,less is dissolved and/or rinsed off than in the case of activating coatswhich have not undergone intermediate drying, and therefore a thickerremaining activating coat is available for the subsequent activation.Consequences here may arise from the compaction of the activating coat,the low or absent water content of the activating coat, the moresignificant formation of the interface on the activating coat, acrystallization, or greater crystallization, of the activating agent,and/or filming and/or crosslinking of the substances of the activatingcoat. In the case of salt-based activating coats in particular,intermediate drying is often necessary.

As an alternative or in addition to intermediate drying it is possibleto use an activating agent which comprises at least one substancemodified with attachment groups, such as a polyelectrolyte modified withattachment groups, and its activating coat formed therefrom is likewisedissolved and/or rinsed off to a lower extent, during rinsing, than anactivating coat with unmodified substances.

Rinsing may serve to remove excess substances and/or impurities such as,for example, salts and/or activating agent which in spite of drying hasnot yet dried. The rinsing liquid uses preferably water or a diluteaqueous solution, more preferably deionized water.

Since a liquid composition such as an activating agent, for example, ora composition to form a secondary coat may not run off completely aftercoating, in depressions in substrates of complex shape that are to becoated, such as bodies in automobile construction, for example, it ispossible that without a subsequent rinsing step, with a water rinse, forexample, there will be an accumulation of the activating agent andexcessively thick coatings in these depressions, and there will beinstances of splashing, all of which may lead to instances ofnonuniformity and paint defects. It is therefore advantageous for thesubstrates coated with an activating agent and/or with a secondary coatto be rinsed after they have been coated. This rinsing is carried outusing, in particular, water, deionized water or an aqueous rinsingsolution. The aqueous rinsing solution may comprise, for example, asalt, an acid, a basic compound and/or an auxiliary such as acrosslinker, for example. In this way it is possible for the surface ofthe coat that is to be rinsed to be chemically influenced and/ormodified.

A further possibility for improving the rinse resistance of theactivating coat is to optimize the rinsing conditions of the type ofrinsing, rinsing speed, rinsing amount, rinsing intensity, rinsingduration and/or flow.

In the case of the rinsing of a rinse-resistant activating coat it isdesirable after rinsing for there still to be at least 5 nm=0.005 μm orat least 0.02 μm of the original or, where appropriate, thetheoretically producible dry film thickness—since often there is nodrying or the drying that there is not sufficient to produce a dryfilm—as measured under a scanning electron microscope. This residualcoat thickness is typically sufficient for activation. The residual coatthickness of the activating coat that remains after rinsing ispreferably from 0.02 to 5 μm or from 0.05 to 2.5 μm or from 0.1 to 1.5μm or from 0.2 to 1 μm. Frequently around 5% to 95%, often 20% to 80% or40% to 60% of the original dry film thickness is eroded during rinsingof the activating coat.

In some embodiments 80% to 100% of the original activating coat isretained during rinsing and after rinsing.

In the case of the method of the invention, rinsing of the activatingcoat and/or rinsing of the secondary coat may take place preferably witha running and/or in a flowing aqueous rinsing liquid by means, forexample, of rinsing off, spray rinsing and/or dip rinsing. Rinsing maymore particularly take the form of dip rinsing, preferably by dipping ina still or moving bath, or the form of spray rinsing, by spraying ontothe surface that is to be rinsed, for example, and/or by the surface tobe rinsed being rinsed off. With each rinsing, it is possible to carryout multiple rinsing as and when required—for example, at least oncewith deionized water.

The residual amounts of the activating coat which are obtained after atleast one rinsing with water, more particular deionized water, make itclear that in spite of intense rinsing, sufficiently high amounts of theactivating coat of the invention are retained. These amounts aresufficient to provide the activated surface with effective preparationfor the subsequent treatment steps.

In accordance with the invention it has been found that if a very highfraction of the activating coat has been retained during rinsing, thedeposition thickness and the deposition rate have been improvedapproximately in proportion to the thickness of the activating coat.

In the case of contact between the remaining activating coat and theaqueous composition to form the secondary coat, activation occurs.Activation via the activating coat provides the prerequisite here forprecipitation, for salting out and/or for deposition of particles.

In the present specification, a dry film thickness for the secondarycoat of more than 1, of more than 2 μm, of more than 4 μm, of more than6 μm, of more than 8 μm, of more than 10 μm, or even of more than 12 μmis preferred.

For certain industrial processes and systems it is particularlyadvantageous if at least one rinse-resistant secondary coat is formed.The at least one secondary coat (=precipitation coat), which in manyvariant embodiments is preferably also rinse-resistant, may also beformed from the substances of at least one activating coat and at leastone secondary coat. The secondary coat may also be formed from at leasttwo individual secondary coats, possibly having different chemicalcompositions.

In principle the aqueous composition to form the secondary coat may beapplied for example by rolling, flow coating, knife coating, injecting,spraying, brushing and/or dipping, including, for example, dipping ofthe aqueous composition at elevated temperature, and optionally bysubsequent squeezing-off, with a roller, for example. Particularlypreferred, for this contacting and coating as well, is application by adipping process.

Preferably at least 90% by weight of the solids and active ingredientsin the aqueous composition to form the secondary coat (=precipitationcoat) comprises constituents which can be precipitated, deposited and/orsalted out and which are anionically, zwitterionically, stericallyand/or cationically stabilized, where anionically and cationicallystabilized constituents do not adversely affect one another, morepreferably to an extent of at least 92%, 94%, 96%, 98%, 99% or 100% byweight.

The aqueous composition to form the secondary coat (=precipitation coat)preferably comprises at least one substance which by virtue of beingactivated with the activating substances of the remaining activatingcoat can be precipitated, salted out and/or deposited.

With particular preference the aqueous composition to form the secondarycoat comprises at least one dispersion and/or at least one formulationsuch as a paint formulation, for example. It is particularly preferredhere in step VI. for the aqueous compositions to be formulations and/ordispersions to form an organic secondary coat, which are selected fromthe group consisting of the following aqueous compositions:

-   -   A) anionically stabilized polymer particle dispersions,    -   B) anionically stabilized formulations,    -   C) sterically stabilized polymer particle dispersions,    -   D) sterically stabilized formulations,    -   E) zwitterionically stabilized polymer particle dispersions,    -   F) zwitterionically stabilized formulations and mixtures thereof    -   or from:    -   G) cationically stabilized polymer particle dispersions,    -   H) cationically stabilized formulations,    -   I) sterically stabilized polymer particle dispersions,    -   J) sterically stabilized formulations,    -   K) zwitterionically stabilized polymer particle dispersions,    -   L) zwitterionically stabilized formulations and mixtures        thereof.

Especially preferred here are A), B) and mixtures thereof, and also G)and H) and mixtures thereof.

The aqueous composition to form an organic secondary coat morepreferably comprises preferably organic polymers and/or copolymers basedon polyvinyl alcohols, polyvinyl acetates, polybutyl acrylates and/orother polyacrylates, polyepoxide esters, polyacrylamides, polyacrylicacids, polycarbonates, polyesters, polyethers, polystyrene-butadienes,poly(meth)acrylic esters, polyvinyl acetate copolymers with acrylicesters and/or copolymers with dibutyl maleate and/or with vinyl estersof at least one Koch acid, polyethylenes, polyvinyl chlorides,polyacrylonitriles, polyepoxides, polyurethanes, polyacrylates,polymethacrylates, polyesters, polyamides, polytetrafluoroethylenes,polyisobutadienes, polyisoprenes, silicones, silicone rubbers and/orderivatives thereof. These polymers and/or copolymers are present in theaqueous composition at, in particular, at least 40% by weight of thesolids and active ingredients.

With particular preference the aqueous composition to form the secondarycoat (=precipitation coat) comprises a dispersion which at least onekind of stabilized polymer particles selected from the abovementionedorganic polymers and/or copolymers and optionally also at least onecorrosion-inhibiting inorganic pigment.

For precipitation, salting out and/or deposition to be able to occur, itis frequently necessary to have a minimum activating coat thickness onthe substrate surface of at least 5 nm dry film thickness.

The aqueous composition to form the secondary coat, after contact withthe activating coat, frequently comprises a low level of activatingsubstances, which are often likewise incorporated into the secondarycoat. In that case the precipitated substances may also comprise thesubstances that precipitate.

The aqueous composition to form a secondary coat preferably includes anamount of solids and active ingredients in the range from 1% to 60% byweight, from 2% to 50% by weight, from 3% to 40% by weight, from 5% to30% by weight, from 6% to 24% by weight, from 7% to 20% by weight orfrom 8% to 16% by weight of the total aqueous composition. The amount ofsolids and active ingredients therein is preferably in the range from 10to 600 g/L, from 18 to 480 g/L, from 24 to 360 g/L, from 28 to 320 g/L,from 32 to 280 g/L, from 36 to 240 g/L, from 40 to 200 g/L, from 44 to160 g/L, from 48 to 120 g/L or from 52 to 80 g/L. In other embodimentsthe amount of solids and active ingredients therein is preferably in therange from 10 to 400 g/L, from 14 to 350 g/L, from 18 to 310 g/L, from22 to 290 g/L, from 26 to 260 g/L, from 30 to 230 g/L, from 34 to 205g/L, from 38 to 180 g/L, from 42 to 155 g/L, from 46 to 130 g/L, from 50to 105 g/L or from 54 to 70 g/L.

The aqueous composition to form the secondary coat, and also thesecondary coat formed therefrom, often comprise primarily polymers,copolymers and/or mixtures thereof. In certain embodiments, particularlyin the case of formulations, they preferably comprise 90% to 100% byweight of the solids and active ingredients.

The secondary coat comprises the precipitated, salted-out and/ordeposited substances optionally with a fraction of the activatingsubstances, preferably in an amount in the range from 90% to 100% byweight or from 95% to 99% by weight.

There may be many substances among the substances of an aqueouscomposition to form a secondary coat, that can be precipitated,coagulated, salted out and/or deposited.

In this context, for example, in particular the stabilized fractions ofthe precipitable substances of the aqueous composition are precipitated,salted out and/or deposited from that aqueous composition, especially ifthe stabilization is eliminated (if destabilization is carried out). Inthat case it is advantageous if the activating substances of theactivating coat within up to 15 minutes or even within up to 5 minutesprecipitate, salt out and/or deposit the substances that are to beprecipitated and, in so doing, form secondary coats which where possiblehave a dry film thickness, after drying, of more than 10 μm. In thiscontext it is possible to salt out the stabilization of the particlesand carry out optional incorporation into the secondary coat. It shouldbe ensured that as far as possible no corrosive or corrosion-promotingconstituents are incorporated into the secondary coat. It isadvantageous for the secondary coat formed to be a very largelyhomogeneous and impervious coating.

Stabilized polymeric substances, in particular, are precipitated here.At the same time there is often destabilization of these substances. Theprecipitated products are frequently X-ray-amorphous.

The substances in an aqueous composition to form a secondary coat thatcan be salted out may include nonpolymeric ionic substances such assalts, for example. The salted-out products are frequently crystalline.In this context it is advantageous for the salt formed to have a lowsolubility in water. A calcium sulfate, for example, has provenparticularly appropriate here.

The substances in an aqueous composition to form a secondary coat thatcan be deposited may include many substances such as, for example, allkinds of inorganic nanoparticles, inorganic colloids, and inorganicpigments, more preferably stabilized particles. For example, inparticular, oxides such as those based on SiO₂ and silicates, moreparticularly phyllosilicates, are deposited from the aqueous compositionto form a secondary coat. The deposited products may be crystallineand/or X-ray-amorphous and also water-insoluble.

The aqueous composition to form the secondary coat preferably includesan amount of precipitable stabilized polymeric substances of in therange from 60% to 100% by weight of the solids and active ingredients,preferably in the range from 70% to 99% or from 80% to 95% or from 88%to 92% by weight of the solids and active ingredients. The aqueouscomposition to form the secondary coat preferably includes an amount ofprecipitable stabilized polymeric substances in the range from 1 to 400g/L or more preferably from 5 to 300 g/L, from 10 to 240 g/L, from 20 to210 g/L, from 30 to 180 g/L, from 40 to 150 g/L, from 50 to 120 g/L, orfrom 60 to 90 g/L.

The aqueous composition to form the secondary coat preferably includesan amount of substances which can be salted out in the range from 1 to200 g/L or more preferably from 5 to 160 g/L, from 10 to 120 g/L, from20 to 90 g/L, or from 30 to 60 g/L.

The aqueous composition to form the secondary coat preferably includesan amount of depositable substances in the range from 0.1% to 50% byweight, more preferably in the range from 1% to 40% or from 3% to 30% orfrom 5% to 25% or from 8% to 21% or from 10% to 18% by weight of thedepositable substances. The aqueous composition to form the secondarycoat preferably includes an amount of depositable substances in therange from 1 to 200 g/L or with particular preference from 5 to 160 g/L,from 10 to 120 g/L, from 20 to 90 g/L, or from 30 to 60 g/L.

It is preferred to use an aqueous composition with a combination ofdifferent kinds of activating substances, such as, for example, of atleast one polyelectrolyte, in particular as matrix substance(s), with atleast one polyvalent salt.

Subsequently a secondary coat is applied to the at least one activatingcoat. The compositions that are used for producing a secondary coatconsist of or comprise preferably at least one aqueous dispersion, moreparticularly at least one stable dispersion, and/or at least one aqueousformulation, more particularly at least one stable formulation, morepreferably a paint formulation or a stable paint formulation. Besideswater, this composition may optionally comprise constituents of anorganic solvent such as at least one alcohol, at least one ether and/oran organic solvent with poor or no water-solubility, such as a furan, atleast one kind of organic and/or inorganic particles, at least onesubstance which influences the pH value, such as acid, for example, suchas carboxylic acid and/or fatty acid, such as acetic acid and/or mineralacid, ammonia, amine, derivatives thereof, stabilized forms thereof andadditives, including paint additives, such as, for example, an organicand/or inorganic crosslinker, a photoinitiator, an adhesion promotersuch as one based on silane/siloxane, a dispersant, a lubricant such aswax, a film-forming assistant, a wetting agent such as one based onpolysiloxanes, a protective colloid, an emulsifier, an organic and/orinorganic corrosion inhibitor, a defoamer, a preservative and/or abiocide.

Polymers and/or copolymers used in the aqueous composition to form thesecondary coat and/or in the secondary coat formed therefrom, in themethod of the invention, may be organic polymers and/or copolymers,based more particularly on alkyd resin, aminoplast resins, epoxide,ethylene-acrylate, alkyl (meth)acrylate, polyethylene, polyisobutylene,polyacrylonitrile, polyvinyl chloride, poly(meth)acrylate, polyalkyl(meth)acrylate such as, for example, polymethyl methacrylate, polyvinylacetate, polyvinyl alcohol, polyvinylidene chloride,polytetrafluoroethylene, polyisoprene, polypropylene,poly(meth)acrylate, polyester, polyether, polyurethane, phenolic resin,polycarbonate, polyamide, polystyrene, polysulfide, siloxane with up toabout 30 monomer units per molecule (=degree of condensation),polysiloxane, polyvinyl acetal, polyacetal, styrene acrylate,derivatives thereof, compounded forms thereof and/or mixtures thereof.The organic substances are frequently in particulate form, especially indispersions. As and when necessary, a formulation may comprise at leastone dispersion. In the case of dispersions and of certain formulationsit is preferred for them to have an acid number in the range from 5 to200, more particularly in the range from 8 to 60 or from 10 to 35.Aqueous compositions which are used more particularly as solutions oforganic polymers and are optionally dried down and/or chemicallymodified may also have acid numbers in the range from 5 to 1000.

The aqueous composition to form a secondary coat preferably includes anamount of organic polymers and/or copolymers in the range from 40% to100% by weight, from 46% to 98% by weight, from 52% to 95% by weight,from 58% to 92% by weight, from 64% to 88% by weight, from 68% to 82% byweight, or from 72% to 76% by weight of the solids and activeingredients in the aqueous composition. The amount of organic polymersand/or copolymers therein is preferably in the range from 10 to 600 g/L,from 18 to 480 g/L, from 24 to 360 g/L, from 28 to 320 g/L, from 32 to280 g/L, from 36 to 240 g/L, from 40 to 200 g/L, from 44 to 160 g/L,from 48 to 120 g/L, or from 52 to 80 g/L. In other embodiments theamount of organic polymers and/or copolymers therein is preferably inthe range from 10 to 400 g/L, from 14 to 350 g/L, from 18 to 310 g/L,from 22 to 290 g/L, from 26 to 260 g/L, from 30 to 230 g/L, from 34 to205 g/L, from 38 to 180 g/L, from 42 to 155 g/L, from 46 to 130 g/L,from 50 to 105 g/L, or from 54 to 70 g/L.

The aqueous composition to form the secondary coat (=precipitation coat)very preferably comprises at least one organic stabilized binder, atleast one corrosion-inhibiting pigment, and optionally at least oneadditive such as, in particular, a thickener, and also, optionally, alow amount of organic solvent. In certain embodiments the aqueouscomposition to form the secondary coat will comprise two or threeorganic stabilized binders, at least one color-imparting pigment, and atleast one corrosion-inhibiting pigment. In individual embodiments it hasbeen found appropriate to use organic polymer dispersions and/orformulations which include, more particularly, graphite and/or carbonblack, in order to mimic the typical gray color of a cathodic depositioncoating.

The organic polymers and/or copolymers in the aqueous composition toform a secondary coat are commonly in the form of stabilized dispersionsor of stabilized formulations. They are customarily in particulate form.Stabilization may be accomplished sterically and/or electrostatically,and is usually brought about using at least one emulsifier. Since thestabilization when using commercial dispersions or commercialformulations is typically unknown, and neither the degree ofstabilization nor the fractions of steric and electrostaticstabilization are known, and can hardly be measured, success in forminga secondary coating, in particular by precipitation and coagulation,cannot be predicted, and so the quality of the precipitation,coagulation, salting-out and/or deposition of the secondary coat cannotbe predicted and cannot be derived, but instead can only be determinedexperimentally.

The stabilization of particles in an aqueous phase, such as a colloidaldistribution of the particles dispersed in a continuous phase, forexample, is accomplished stably provided the particles are held apart byforces of repulsion. Fundamental stabilization mechanisms that areactive here are electrostatic stabilization and/or steric stabilization.For electrostatic stabilization, there must be charges present on thesurface of the particles. Steric stabilization occurs whenmacromolecules are attached to the particle surface and when the shellsof the particles are unable to move substantially into one another.Accordingly, the particles remain at a distance from one another suchthat, for example, a dispersion is stable.

Molecules referred to as zwitterionic are those which possess not onlynegatively charged but also positively charged functional groups. Thezwitterionic surfactants, which can be used to stabilize particles inaqueous solutions, have a polar moiety and an apolar moiety. Neutralsubstances known include nonionic surfactants and all organic moleculeswhich do not carry any groups with anionic character.

In this context it is preferred for substances to be selected in eachcase, and combined in the method of the invention, that have chemicalaffinity between activating agent and the substances for forming thesecondary coat.

The aqueous composition to form a secondary coat and also the secondarycoat formed therefrom frequently comprise predominantly polymers,copolymers and/or mixtures thereof. In some embodiments, especially inthe case of formulations, they preferably comprise 0.1% to 45% byweight, based on the solids and active ingredients, of one or moreinorganic substances, more particularly 1% to 30% or 6% to 15% byweight.

Inorganic substances which may be present depending on the procedure,profile of properties of the secondary coat, and intended applicationfor the coated substrate, are preferably color pigments, white pigmentssuch as those based on TiO₂, for example, amorphous dyes, fillers,inorganic fibers, and/or anticorrosion pigments with weak solubility inwater, such as those based on silica(s), oxide(s) and/or silicate(s),for example, such as anticorrosion pigment(s) containing alkaline earthmetals, such as calcium-modified silica and/or alkaline earth metalsilicate.

The amount of organic solvents in the aqueous composition to form asecondary coat may be 0% or 0.01% to 5% or 0.1% to 1% by weight of theliquid composition, based on the liquid composition.

Particles which can be used in the context of the method of theinvention are any of a wide variety of types of particle, particlesizes, and particle shapes.

As particles in the aqueous composition to form the secondary coatand/or in the secondary coat formed therefrom it is possible withpreference to use oxides, hydroxides, carbonates, phosphates,phosphosilicates, silicates, sulfates, organic polymers includingcopolymers and derivatives thereof, waxes and/or compounded particles,especially those based on anticorrosion pigments, organic polymers,waxes and/or compounded particles, and/or mixtures thereof. Theypreferably have particle sizes in the range from 5 nm to 15 μm, from 8nm to 5 μm, from 12 nm to 3 μm or from 15 nm to 1.5 μm, moreparticularly from 20 nm to 1 μm, from 30 nm to 700 nm, from 40 nm to 600nm, or from 50 nm to 500 nm. They are preferably water-insolubleparticles.

The water-insoluble particles include, among others, stabilizedparticles where the stabilization takes place in the aqueous phaseand/or is present in the aqueous phase, and can be achieved preferablyon the particle surface, for example with a nonionic and/or ionicemulsifier, with ions, with a flow control agent and/or with athickener.

Compounded particles feature in one particle a mixture of at least twodifferent substances. Compounded particles may often have othersubstances having very different properties. They may, for example,comprise in whole or in part the composition for a paint, perhaps evenwith the presence of substances of non-particulate form, such as, forexample, surfactant, defoamer, dispersant, paint auxiliary, other kindsof additives, dye, corrosion inhibitor, weakly water-solubleanticorrosion pigment and/or other substances which are customary and/orknown for such mixtures. Paint constituents of these kinds may besuitable and/or frequently utilized, for example, for organic coatingsfor forming, for anticorrosion primers and other primers, for paints,surfacers and/or clearcoat materials.

Generally in this context it is frequently preferred to use a) a mixtureof chemically and/or physically different particles, b) particles,aggregates and/or agglomerates of chemically and/or physically differentparticles, and/or c) compounded particles, in the aqueous composition toform the secondary coat and/or in the secondary coat formed therefrom.

An anticorrosion primer frequently has electrically conductive particlesand in the case of a high fraction of such particles can be electricallywelded even at coat thicknesses in the range, for example, of 3 to 10μm.

In many cases it is preferred for a particle-comprising aqueouscomposition and/or the secondary coat formed from it to comprise notonly at least one kind of particles but also at least one nonparticulatesubstance, more particularly additives, dyes, corrosion inhibitorsand/or weakly water-soluble anticorrosion pigments. As particles in anaqueous composition to form the secondary coat and/or in the secondarycoat formed therefrom it is also possible, for example, for coloredand/or electrically conductive particles, based in particular on oxideparticles with electrically conducting coatings, iron phosphide, ironoxide, fullerenes and other carbon compounds with graphite-likestructures and/or carbon black, optionally including nanocontainersand/or nanotubes, to be present. On the other hand it is possible heremore particularly to make use, as particles in the composition and/or inthe coating formed from it, of coated particles, chemically and/orphysically modified particles, core-shell particles, compoundedparticles comprising substances of different kinds, encapsulatedparticles, nanocontainers and/or nanotraps.

In one embodiment of the method of the invention it is preferred for theparticle-comprising aqueous composition to form a secondary coat, thesecondary coat formed therefrom and/or the coating formed therefrom bymeans for example of filming and/or crosslinking to comprise not only atleast one kind of particles but also in each case at least one dye,color pigment, anticorrosion pigment, corrosion inhibitor, conductivitypigment, other kind of particles, silane/silanol/siloxane, polysiloxane,silazane/polysilazane, paint additive and/or additive such as, forexample, in each case at least one surfactant, one defoamer and/or onedispersant.

In the method of the invention it is preferred for the compositionand/or the coating formed therefrom to have not only at least one kindof particles and optionally, besides at least one nonparticularsubstance, partly or completely, a chemical composition for a primer, apaint such as, for example, for a surfacer, topcoat and/or clearcoatmaterial.

Particles which can be used in the aqueous composition to form asecondary coat in the method of the invention, especially when theintention is first to form a particle-rich secondary coat from thecomposition, are, in particular, particles based on alkyd resin,aminoplast resins, epoxide, ethylene-acrylate, alkyl (meth)acrylate,polyethylene, polyisobutylene, polyacrylonitrile, polyvinyl chloride,poly(meth)acrylate, polyalkyl (meth)acrylate such as, for example,polymethyl methacrylate, polyvinyl acetate, polyvinyl alcohol,polyvinylidene chloride, polytetrafluoroethylene, polyisoprene,polypropylene, poly(meth)acrylate, polyester, polyether, polyurethane,phenolic resin, polycarbonate, polyamide, polystyrene, polysulfide,siloxane with up to about 30 monomer units per molecule (=degree ofcondensation), polysiloxane, polyvinyl acetal, polyacetal, styreneacrylate, derivatives thereof, compounded forms thereof and/or mixturesthereof. In the case of particle-rich secondary coats as well, filmingof the coating may be particularly advantageous. The reason is that allof the substances may be present in particular form.

As additions to the organic polymers and copolymers in the form ofparticles it is advisable in numerous embodiments to have pigmentsand/or additives of the kind frequently used in paints and/or primers.

The aqueous composition to form the secondary coat preferably has adynamic viscosity in the range from 1 to 10 000 mPa s; more preferablyit has a viscosity in the range from 4 to 5000 or from 8 to 1200 mPa s,very preferably in the range from 15 to 800, from 20 to 450, from 40 to350, or from 60 to 250 mPa s, in each case as measured using a PhysicaMCR 300 Modular Compact Rheometer model rotary viscometer from PaarPhysica in accordance with DIN EN ISO 3219.

The pH value of the aqueous composition to form a secondary coat mayvary within wide limits and/or may be adapted to the appropriate pHvalues. The pH value is preferably in the range from 4 to 12, morepreferably in the range from 6 to 11, from 7 to 10, or from 7.5 to 9.

One way to improve the deposition of a secondary coat and/or to improvethe secondary coat is the chemical modification of the substances in thesecondary coat using, for example, silane/silanol/siloxane and/or otherattachment groups. Another way of improving the deposition of asecondary coat and/or for improving the secondary coat is to use a lowelectrical auxiliary voltage in the course of precipitation, salting-outand/or deposition for applying a secondary coat. In this case it isparticularly preferred to apply an auxiliary voltage of less than 2.5 V,of less than 1 V, or of less than 0.5 V, more particularly as directcurrent, in which case there is preferably virtually no current flow. Inthe event of a current flow, the current strength is less than 0.1 A/dm²or preferably less than 0.01 A/dm². The auxiliary voltage here may havethe effect, for example, of accelerating ion migration, but not ofinitiating precipitation, deposition and/or salting out. This auxiliaryvoltage may accelerate the formation of the coat and/or enhance the coatquality. In the majority of embodiments, however, no electrical voltageis applied from the outside. If a deposition coating is to be applied,it is possible to operate electrolessly or, optionally, with anelectrical auxiliary voltage, but in contrast to the situation with anelectrodeposition coating material, the electrical auxiliary voltage isnot used primarily for precipitation, deposition and/or salting-out ofan aqueous composition. The evident effect of the electrical auxiliaryvoltage is that of particle migration and hence of an increase inconcentration of, for example, the substances to be precipitated and/orthe particles to be coagulated, but it does not result in separation ofwater and solids present therein on the basis of the electrical fieldand current, as is the case with application of an electrodepositioncoating material.

Coating with a secondary coat may take place preferably at compositiontemperatures between 5 and 95° C., more preferably at room temperature,or at temperatures between 15 and 50° C. In this case, in a number ofembodiments, the substrate may have a temperature in the range from 10to 120° C. and more particularly in the range from 25 to 95° C. or from40 to 70° C.

Coating with the aqueous composition to form the secondary coat may takeplace by any mode of application, more particularly, for example, byspraying, dipping, rolling, etc.

In certain embodiments of the present invention this coating techniqueis a self-regulating technique, and so a coating is formed only for acertain time and in accordance, for example, with the coagulationpotential of the activating coat—irrespective of the duration of contactwith the solution for the secondary coat.

Rinsing, especially of the secondary coat that is only slightly,partially dried, is as yet undried and/or is freshly applied, may beadvantageous in order to reduce the amount of impurities and excessivefractions of substances which have not been precipitated, salted outand/or deposited (wet-on-wet method). It can help to remove residualamounts of corrosive substances.

It also helps to adapt a method of the invention in analogy to anexisting dipping process.

If, however, the applied secondary coat is not rinsed prior to drying,this may result in an uneven coating, possibly with more poorly bakingand/or more poorly crosslinking portions, in a coating with pooreradhesion of the secondary coat to a subsequent coating, and/or in asecondary coat having lower corrosion resistance.

In one embodiment of the method of the invention it is preferred for thesecondary coat to be rinsed at least once with a rinsing liquid such aswater and/or an aqueous afterrinse liquid, and thereafter to be coated,preferably in the wet, damp, partially dried or no more greatly driedstate, with at least one organic composition, such as a primer and/orpaint.

The secondary coat can be dried in a variety of ways, optionally afterat least one rinse. Drying may take place in any conventional way and inall known dryers, but also with infrared radiation, with NIR radiation,with forced air, with fresh-air feed, etc. Particularly preferred is adrying operation with high gas and/or air throughput, in order to removethe high level of water vapor. Drying must be adapted appropriately tothe physical composition and thickness of the secondary coat to bedried, and also to the nature of the coating line and its speed, inorder that, as far as possible, there are no cracks, incipient cracks,delaminations, pops or other defects occurring.

The secondary coat is preferably filmed and/or crosslinked in order toform a very largely impervious coating that also, in the case ofmetallic substrate, it is corrosion-resistant. Drying may take place inparticular in a temperature range from 10 to 170° C., preferably in arange from 15 to 140 or from 20 to 120 or from 25 to 90 or from 30 to80° C., more preferably above 50 or 70° C. to 130 or to 95° C. Filmingand/or crosslinking may take place in particular during drying and/orheating. Crosslinking may also take place wholly or partly by radicalpolymerization and/or additionally by an aftercrosslinking procedure—athermal aftercrosslinking procedure, for example. The crosslinkingprocesses are known in principle. At elevated temperature, filming willtypically occur. A film-forming assistant may also help to ensure thatin the course of drying, a solidifying surface layer is formed on thesecondary coat, such a layer being a hindrance to further egress ofwater vapor.

The extent to which filming and/or crosslinking takes place is dependenton the chemical construction of the composition used and on the chemicalconstruction of the secondary coat formed from that composition, and inprinciple is familiar to the skilled person, meaning that there is noneed for a further description here.

By filming is meant the formation of a film from a material with a highorganic fraction, such as a polymer dispersion, in the course of which,in particular, polymer particles undergo transition, preferably at roomtemperature or slightly elevated temperature, into a uniform film. Oftenin this context there is talk of coalescence of the comparatively largepolymer particles. Filming in this context takes place from an aqueousmedium, during drying, and optionally with plasticization of the polymerparticles by means of the film-forming assistants that remain. Filmformation can be improved and/or enabled by the use of soft syntheticresin (König Pendulum hardness at room temperature in accordance withDIN EN ISO 1522 measured at less than 30 s) and/or by addition ofsubstances which act as temporary plasticizers (=film-formingassistants). Film-forming assistants act as specific solvents whichsoften the surface of the polymer particles and so allow them to bealtered geometrically by coalescence of the organic particles with oneanother, but which in particular do not have short-term volatility and,in particular, undergo primarily evaporation, after the evaporation ofthe water, and preferably do not remain durably in the film. In thiscase the resultant film is often pore-free or substantially pore-free,and may include undissolved and/or insoluble particles such as inorganicparticles, for example. It is advantageous here for these plasticizerson the one hand to remain in the aqueous composition for a sufficientlylong time to be able to act on the polymer particles for a long time,and thereafter to evaporate and thus escape from the film. In the caseof appropriate film formation, in many variant embodiments, atransparent film is formed, but not a milky white or even powdery film,which is a sign of disrupted film formation. For perfect or near-perfectfilm formation, the temperature of the wet film applied to a surfacemust lie above the minimum filming temperature (MFT). Only in that caseare the polymer particles soft enough to coalesce. It is particularlyadvantageous here if the film-forming assistants as temporaryplasticizers do not alter, or virtually do not alter, the pH value ofthe aqueous composition.

Film formation can be improved by the use of thermoplastic polymersand/or copolymers and/or by addition of substances which serve astemporary plasticizers. These last-mentioned film-forming assistants actas specific solvents, which soften the surface of the polymer particlesof a dispersion or formulation and so allow it to coalesce. In thiscontext it is advantageous if these plasticizers remain in the aqueouscomposition for a sufficiently long time on the one hand in order to acton the polymer particles for a long time, and thereafter evaporate andhence escape from the film. It is further advantageous if residual wateris also present for a sufficiently long time during the dryingprocedure.

The at least one film-forming assistant, which is or has been added inthe form of at least one long-chain alcohol, serves for improving filmformation particularly in the course of drying. From the organic filmformer, together with at least one long-chain alcohol, in particularduring and/or after the loss of water and other volatile constituents, alargely or entirely homogeneous organic film is formed by filming. Forbetter film formation of the polymeric particles of the aqueouscomposition during drying, it is possible to use, particularly as atemporary plasticizer for the polymer particles, at least one long-chainalcohol, preferably a butanediol and derivatives thereof, based moreparticularly on triethylene glycol, tripropylene glycol and/orderivatives thereof.

The amount of at least one film-forming assistant in the aqueouscomposition—more particularly in the bath—may be preferably 0.01 to 50g/L, based on solids including active ingredients, more preferably 0.08to 35 g/L, very preferably 0.2 to 25 g/L, 0.3 to 20 g/L, or 0.5 to 16g/L, more particularly 1 to 12 g/L, 2 to 10 g/L, 3 to 8 g/L, or 4 to 6g/L. The weight ratio of the amounts of organic film former to amountsof film-forming assistants in the aqueous composition—more particularlyin the bath—may vary within wide ranges; more particularly, it may be(100:0.1). This ratio is preferably in the range from 100:10 to 100:0.2,from 100:5 to 100:0.4, or from 100:2.5 to 100:0.6, more preferably inthe range from 100:2 to 100:0.75, from 100:1.6 to 100:0.9 or from100:1.4 to 100:1.

Often a mixture of at least two film-forming assistants is used. Thefilm-forming assistants preferably have a boiling point at 760 mm Hg inthe range from 140 to 400° C., more particularly in the range from 150to 340° C., from 160 to 310° C. or from 170 to 280° C., and/or anevaporation index for ether=1 in the range from 100 to 5000, moreparticularly in the range from 120 to 4000, from 135 to 2800, or from150 to 1600.

Especially advantageous as film-forming assistants are alcohols such as,for example, diols and also their ethers and esters having moreparticularly 4 to 20 or having 6 to 18 or having 8 to 16 C atoms,preferably alcohols, ethylene glycol ethers, and propylene glycol ethershaving more particularly 4 to 20 or having 6 to 18 or having 8 to 16 Catoms.

Film-forming assistants which can be used in one preferred variant ofthe invention are selected from the group consisting of butanediol,butyl glycol, butyl diglycol, ethylene glycol ethers such as ethyleneglycol monobutyl ether, ethylene glycol monoethyl ether, ethylene glycolmonomethyl ether, ethyl glycol propyl ether, ethylene glycol hexylether, diethylene glycol methyl ether, diethylene glycol ethyl ether,diethylene glycol butyl ether, diethylene glycol hexyl ether,polypropylene glycol ethers such as propylene glycol monomethyl ether,dipropylene glycol monomethyl ether, tripropylene glycol monomethylether, propylene glycol monobutyl ether, dipropylene glycol monobutylether, tripropylene glycol monobutyl ether, propylene glycol monopropylether, dipropylene glycol monopropyl ether, tripropylene glycolmonopropyl ether, propylene glycol phenyl ether, trimethylpentanedioldiisobutyrate, polytetrahydrofuran(s), polyether polyol(s) polyesterpolyol(s), and also derivatives thereof and mixtures thereof. They arepresent preferably in an amount in the range from 0.1 to 30 g/L, basedon solids including active ingredients, and more preferably in an amountin the range from 1 to 10 g/L or from 2 to 5 g/L in the aqueouscomposition.

In contrast to filming, which may take place at comparatively lowtemperatures such as, for example, at temperatures in the range aboveabout 5° C., temperatures of at least 50° C. are normally needed for thecrosslinking for organic coatings which crosslink chemically orchemically-thermally. It is preferred to select film-forming assistantsand to add them in an amount such that the composition films preferablyat temperatures greater than 5° C., more preferably greater than 10° C.,greater than 20° C., or greater than 40° C., more particularly greaterthan 60° C., greater than 80° C., greater than 100° C., or greater than120° C. Accordingly it is preferred for the minimum film-formingtemperature of the synthetic resins, including film-forming assistants,to film at temperatures greater than 40° C., more preferably greaterthan 60° C., greater than 80° C., greater than 100° C., or greater than120° C. The simultaneous and/or subsequent drying takes place preferablyat slightly higher (=at at least 20° C.) or significantly higher,preferably at least 30, 50, 70, 90, or 110° C., temperatures than theminimum film-forming temperature of the synthetic resins, includingfilm-forming assistants. In the course of drying, water and, wherepresent, organic solvents escape. This is usually accompanied by theonset of film formation, where the organic substances, optionally inparticulate form, are able to take up positions more close to oneanother, become softer as a result of the higher temperature, and canform an impervious film. It is particularly preferred for filming totake place to a substantial degree even at room temperature.

Crosslinking, especially of resins, may take place, for example, withcertain reactive groups such as, for example, isocyanate, isocyanurateand/or melamine groups. As crosslinkers it is possible independently ofone another to use the following: inorganic crosslinkers such as thosebased on zirconium compounds, such as ammonium zirconium carbonate, forexample, and/or organometallic crosslinkers such as those based onorganotitanate, such as diisopropyl ditriethanolaminotitanate, forexample, and/or those based on organozirconate, and/or organiccrosslinkers such as adipic dihydrazide, those based on aziridine, suchas polyfunctional polyaziridine, those based on an azo compound, orbased on diamine, or based on diimide, such as multifunctionalpolycarbodiimides, for example, those based on formaldehyde, such asurea-formaldehyde and/or melamine-formaldehyde, those based onimidazole, such as 2-ethyl-4-methylimidazole, those based on isocyanate,those based on isocyanurate, those based on melamine, such as, forexample, methoxymethyl-methylol-melamine and/orhexamethoxymethyl-melamine, those based on peroxide, those based ontriazine, such as, for example, tris(alkoxycarbonylamino)triazine,and/or those based on triazole. They are preferably present in an amountin the range from 0.1 to 30 g/L, based on solids, including activeingredients, and more preferably in an amount in the range from 1 to 10g/L or from 2 to 5 g/L, in the aqueous composition.

It is usual here to use organic crosslinkers based onmelamine-formaldehyde in a temperature range from about 130 to about210° C., preferably in the range from 140 to about 200° C., whereas theother organic crosslinkers are mostly or typically used in a temperaturerange approximately from 50 to about 120° C., preferably in the rangefrom about 60 to about 110 or to about 100° C. These latter crosslinkersare referred to here as organic low-temperature crosslinkers.

The secondary coat is preferably dried in a way such that, inparticular, organic polymer particles that are present, especially asconstituents of a dispersion, are able to film, so forming a largely orentirely homogeneous coating. In some embodiments the dryingtemperatures here can be selected at a sufficiently high level for theorganic polymeric constituents to be able to crosslink.

In the context of the method of the invention, it is preferred incertain embodiments for a secondary coat including a high fraction oforganic particles to be formed; it is preferred for this coat to befilmed and/or crosslinked in the course, for example, of drying. In someembodiments filming takes place even without the presence offilm-forming assistants. In that case the particles of the coating,particularly if they are present predominantly or entirely in the formof organic polymers, can be filmed preferably to form a largely orentirely impervious coating, particularly in the course of drying. Inthis context it is often preferred for the drying temperature of acoating that consists primarily or wholly of organic polymers to beselected such that a largely or entirely impervious coating is formed.As and when necessary, at least one film-forming assistant can be addedfor the purpose of filming, especially an assistant based on at leastone long-chain alcohol. In the case of embodiments having two or moresecondary coats one above another, it is preferred first to apply all ofthe secondary coats in succession and to subject them thereafter, as andwhen necessary, to joint filming and/or crosslinking.

In the context of the present invention it is preferred in many casesfor the drying, filming and/or crosslinking to take place in thetemperature range from 5 to 350° C., from 8 to 200° C., from 10 to 150°C., from 12 to 120° C., or from 14 to 95° C., more preferably in thetemperature range from 16 to 40° C., based on the oven temperatureand/or based on Peak Metal Temperature (PMT). The selected temperaturerange is largely dependent on the nature and amount of the organicconstituents and also, optionally, of the inorganic constituents, andalso, optionally, on their film-forming temperatures and/or crosslinkingtemperatures.

The secondary coat preferably has a wet film thickness in the range from5 to 120 μm or from 10 to 80 or from 15 to 50 μm, and after dryingpreferably has a dry film thickness in the range from 4 to 100 μm, from6 to 80 μm, from 8 to 60 μm, from 10 to 45 μm, from 12 to 32 μm, from 14to 28 μm, from 16 to 25 or from 18 to 20 μm.

In many embodiments, therefore, the quality of the secondary coat isdependent on the one hand substantially on the quality and on thethickness of the activating coat or of the activating coat that remainsafter rinsing, and on the other hand is substantially dependent on thephysicochemical conditions such as, for example, on the consistency andon the composition of the aqueous composition to form the secondarycoat.

It can be advantageous if the at least one activating substance of theactivating coat does not have too high a diffusion rate into the aqueouscomposition when the secondary coat is being formed. The diffusion rateof the at least one activating substance of the activating coat can belimited on the one hand by using relatively large and/or bulkymolecules, examples being the polyelectrolytes and/or chemicallymodified polyelectrolytes, or, on the other hand, by selecting saltshaving a relatively low solubility in water. The temperatures of thesubstrate provided with the activating coat and/or of the aqueouscomposition to form the secondary coat may also be used in order toinfluence the formation of the secondary coat.

The experimental results that exist suggest, surprisingly, that there isan optimum in relation to the formation of very thick secondary coats inthe case of thick activating coats and of aqueous compositions ofcomparatively low concentration and intended to form a secondary coat;above and below this optimum concentration of the aqueous composition,the secondary coats that are formed are not quite so thick.

In the course of the further treatment of the coated substrates it ispossible—as and when appropriate, independently of whether oil has orhas not been applied—for, in particular, alkaline cleaning, acidicpickling and/or water rinsing to take place.

Coating with an anticorrosion primer such as a welding primer, forexample, may allow additional protection from corrosion, particularly incavities and difficult-to-reach parts of a substrate, and may also allowformability and/or joinability in the case, for example, of folding,adhesive bonding and/or welding. Following forming and/or joining, it ispossible, as and when necessary, to employ a further coating, optionallyalso in a procedure according to the invention.

In industrial practice it would be possible for an anticorrosion primerto be used in particular when the substrate coated therewith, such as ametal panel, after being coated with the anticorrosion primer, is formedand/or joined to a further component, and if further coatings are notapplied until after that. If additionally in this procedure ananticorrosion primer is applied beneath the activating coat and beneaththe particle coating, the protection from corrosion that is produced isusually improved significantly.

In the case of rinsing of the substrates coated with activating agentand with the substances of the secondary coat, the intention is often toremove as little as possible of the secondary coat, and it must not beremoved completely. It is therefore advantageous if the activating coatand/or the secondary coat are sufficiently rinse-resistant for suchlines and procedures.

It is particularly preferred to coat the secondary coat, in a wet, dampor only slightly, initially dried state, with a subsequent coating in awet-on-wet process.

Following the application of the activating coat and of the secondarycoat, and optionally after the generation of a largely or entirelyimpervious coating from the activating and/or secondary coat, it ispossible for the coat of an adhesive, primer and/or paint to be appliedto this coat or coating, for example.

In certain embodiments it is particularly preferred, over the largely orentirely impervious coating, to apply at least one coat of a paint oreven a paint system made up for example of basecoat and clearcoat, orany desired paint system. If thereafter a further organic coating isapplied, it can be used to achieve coloration and/or matting or toenable joining. In other embodiments it may be preferable for thesurfaces coated in this way to be formed and/or to be joined to at leastone other component and/or for an adhesive layer and/or at least oneadhesive molding to be applied prior to an adhesive bonding operation.

The treatment steps and the possible compositions before the activatingstep and after the formation of a secondary coat are well known to theskilled person and can be varied diversely.

The problem addressed by the present invention is also solved with acoating produced by the method of the invention.

The coating of the invention can be used with preference for coatedsubstrates in the form of wire, wire mesh, strip, sheet, profile, panel,part of a vehicle or missile, element for a household appliance, elementin the building industry, frame, guideboard element, radiator element orfencing element, molding of complex geometry, or small part such as, forexample, bolt, nut, flange, or spring.

The coating of the invention or the substrate coated in accordance withthe invention is used preferably in vehicle or aircraft construction, inthe building industry, in appliance construction or in heating systems,and more particularly for components for vehicles such as vehiclebodies, for missiles, for architectural applications, for heatingsystems, and for household appliances.

In one embodiment of the method the following are employed:

Optionally a one-stage or multistage cleaning of the substrate, followedby at least one rinsing with water or with an aqueous rinsingliquid—application of an activating coat—at least one rinsing with wateror with an aqueous rinsing liquid—application of a secondary coatcomprising substances of the aqueous composition to form a secondarycoat and optionally also comprising activating agent that hasremained—optionally at least one rinsing with water or with an aqueousrinsing liquid—drying and in this case optionally alsofilming—optionally crosslinking of secondary coat at elevatedtemperature—optionally application of further coatings—optionally bakingand crosslinking—optionally application of further coatings.

In one particular embodiment of the method the following are employed:

Alkaline cleaning of the substrate—rinsing with municipal water—rinsingwith DI water—application of an activating coat—rinsing with DIwater—application of a secondary coat comprising substances of theaqueous composition to form a secondary coat and optionally alsocomprising activating agent that has remained—rinsing with DIwater—drying and in this case optionally also filming—optionally bakingand crosslinking—optionally coating with further organic coating.

It has been found that on the surfaces coated with activating substancein accordance with the invention, subsequently, largely or whollyimpervious secondary coats are formed, which together with theactivating coat that has remained may have a coat thickness even in therange from 2 to 50 μm, more particularly a coat thickness in the rangefrom 3 to 40 μm, from 4 to 30 μm, from 5 to 20 μm, from 6 to 15 μm orfrom 8 to 10 μm, more preferably a coat thickness in the range from 3 to30 μm, from 4 to 25 μm, from 5 to 18 μm, from 6 to 12 μm or from 7 to 10μm. The individual coatings may have such coat thicknesses before and/orafter their filming and/or before their crosslinking.

In comparison to the coating processes described in WO 2010/054985 A1,the results according to the invention show that the present methods aretechnically far less costly and inconvenient and are substantially moreeffective for obtaining dry film thicknesses in the region of at least 2μm, since with the compositions of WO 2010/054985 A1 the precipitationpotential is substantially lower than in the case of the methodsdescribed here, and since a much thicker silane activating coat isnecessary for a certain coat thickness than in the case of the coatingsutilized here that contain activating agent such as, for example, apolyelectrolyte or salt such as a formate, for example. The reason isthat, with the processes of WO 2010/054985 A1, it was possible, even infurther experiments, to obtain total coat thicknesses for the activatingcoat and for the secondary coat together, under conditions that cannormally be applied technically, only of up to 1 or 2 μm (seecomparative examples).

In comparison to this it has been possible, with the present method ofthe invention, with a single secondary coat, to achieve dry filmthicknesses of up to 65 μm; preferred secondary coat thicknesses in therange from 3 to 30 μm have been produced without problems.

It has emerged that the surfaces coated in accordance with theinvention, from which, subsequently, largely or poorly imperviouscoatings were produced, could be produced in a significantly easier andsignificantly more cost-effective way than, for example, electrocoatcoatings, autophoretic deposition coatings or powder coatings.

It has emerged, furthermore, that coatings produced in accordance withthe invention are at least equivalent to the electrocoat, autophoreticdeposition, and powder coatings, in terms of their properties, with acomposition in line with present-day industrial practice.

It has surprisingly been found that the method of the invention can beoperated in a simple way and without costly and inconvenient control; itis normally not necessary to apply any external electrical voltage.

Surprisingly it has been found that even anionic polyelectrolytes canlead to the precipitation of an anionically stabilized dispersion.Surprisingly it has been found that, conversely, even cationicpolyelectrolytes can lead to the precipitation of a cationicallystabilized dispersion.

The method of the invention can be used within a wide temperature rangeand in particular also at room temperature, if the subsequent drying isdisregarded.

It has surprisingly been found that in the method of the invention nocostly and inconvenient control measures are needed, with regard to theapplication of the activating agent, in order to obtain a uniform andhomogeneous coating, and that, for a low level of consumption ofchemicals, high-grade protective secondary coats are formed, which inpreferred embodiments attain a thickness in the range from 500 nm to 30μm.

It has surprisingly been found that the activating coats have been able,by means of corresponding surface-active modifications to the polymericstructure and the incorporation thereof into pretreatment formulations,to be anchored even more rinse-resistantly in the dipping, and withoutintermediate drying of the activating coat beforehand, on cleanedsubstrate surfaces.

It has also been possible to deposit corresponding rinse-resistantsecondary coats by virtue of the activating coats of the invention. Inone variant, the activating coats enabled a wet-on-wet dipping processfor the entire application, consisting of activating coat, secondarycoat, and necessary rinsing steps, and so the method of the inventioncan be employed as a substitute for a coating method with anelectrodeposition coating material.

It has surprisingly been found that the method of the invention is aself-regulating process with regard to the deposition, especially of thesecondary coat, which does not require any costly and inconvenientcontrol measures and with which, at a low level of consumption ofchemicals, high-grade protective coatings are formed.

It has surprisingly been found that the aqueous compositions used, notleast the formulations used, for the deposition of a secondary coat,have been able to be converted, on a surface preconditioned with anactivating coat, not only into largely impervious or fully imperviouscoatings, and into largely homogeneous or fully homogeneous coatings—incontrast to the same aqueous compositions applied to the surface withoutsuch an activating coat, but instead that it has also been possible toanchor the secondary coats rinse-resistantly on the surface.

It has surprisingly been found that depending on the selection of thesubstrate, of the different activating agents, and of the aqueouscomposition to form a secondary coat, it is possible to produce coatingsof the invention which in terms of their paint adhesion and theircorrosion control can be adapted individually to the particularrequirements—for example, to particular levels of corrosion control andpaint adhesion that make sense for the application.

It has surprisingly been found that as a result of the applied coatthickness of activating agent, the resultant coat thickness of thesecondary coat has been able to be influenced in a controlled way: thismeans that a low level of coating with activating agent, remaining afterrinsing, leads to a lower coat thickness for the secondary coat, and,conversely, that a higher coat thickness of activating coat results in acorrespondingly high coat thickness of secondary coat.

In this context it has also been found that the amount of secondary coatapplied does not increase further even when the residence time of thecorrespondingly activated substrates in the bath comprising thesecondary coat is extended (self-regulation); this means that after aresidence time of the activated samples in the bath that forms thesecondary coat, in particular in the range from 1 to 10 minutes, therewas no further increase in the coat thickness of the secondary coat as aresult of a longer residence time of the activated substrates in theaforementioned bath.

In summary it was possible, by means of the coat thickness of theactivating coat and the amount of the solids and active ingredients usedin the secondary coat, to control the resultant complete coat thicknessin a targeted way.

It has surprisingly been found that the secondary coats deposited inaccordance with the invention typically formed homogeneous coats withuniform dry film thicknesses on a workpiece of complex shape, comparablewith the quality of conventional, electrophoretically orautophoretically deposited paint coats.

It has also been surprisingly found that the baths containing theaqueous composition for the secondary coat, in spite of a highthroughput of activated surfaces, exhibited excellent process stability,with no further precipitation reactions being observed apart from thoseon the activated surfaces. Here, after drying, coats of high qualitywere obtained, which are comparable with electrophoretic coatings.

There were therefore no instances of unwanted precipitation in the bathor on the walls of the plants, containers, and stirrer mechanisms, inspite of the high throughput of surfaces provided with activating agent.

A further particularly surprising effect of the present invention wasfound when a polyelectrolyte modified with a silane/silanol/siloxane isused as activating agent for producing the activating coat, especiallyin the case of polyelectrolytes modified with at least one alkoxysilanehaving epoxy and/or isocyanato groups and/or with at least one resultantsilanol and/or siloxane formed therefrom.

In a particular range of proportions of silane(s) to activating agent,particularly good depositions are achieved; outside this range, only theconventional kind of silane deposition was found, but there was nolonger any deposition of the activating agent, especially in the case ofpolyethyleneimines. This effect was found particularly for the reactionof an epoxysilane with a polyethyleneimine having a high molecular massof preferably about 1.5 to 2.5 million Da.

For the case of polyethyleneimine in particular this was verysurprising, since the assumption prior to the present invention, giventhe known reactivity of epoxides and amines, was that an increase in theamount of silane would also lead to ever greater deposition, through tocomplete deposition, of polyethyleneimine. The fact that this is not thecase, however, but that instead it took place only within a certainproportion of silane to polyethyleneimine, was completely unexpected. Inthis context, a molar ratio of polyethyleneimine to silane approximatelyin the range from 1: (1000 to 5000) was used. The polyethyleneimine herewas employed in the form of a randomly branched dendrimer.

Surprisingly it is also possible for anionic polyelectrolytes to lead tothe precipitation of an anionically stabilized dispersion, and cationicpolyelectrolytes can also lead to the precipitation of a cationicallystabilized dispersion.

Also provided by the present invention, accordingly, is the use of apolyelectrolyte modified with at least one silane/silanol/siloxane, inparticular of a polyelectrolyte modified with at least one alkoxysilanehaving epoxy and/or isocyanate groups and/or with at least one silanoland/or siloxane formed therefrom, as activating agent, consisting ofpolyethyleneimine and silane/silanol/siloxane in a ratio of 1:(1000 to5000), calculated on the basis of the silane, in methods for theelectroless coating of substrates, more particularly of metallicsubstrates.

Certain embodiments of the present invention are evident from variantsA) to F) below, which can be combined with one another in any desiredform:

-   A) Method for coating surfaces of substrates which may optionally    have been precoated (=surfaces to be coated) with a first aqueous    composition in the form of a solution, emulsion and/or suspension    which comprises at least one water-dissolved salt and/or    polyelectrolyte (activating agent), to form a first, salt- and/or    polyelectrolyte-containing coat (activating coat), with the first    coat, comprising salt and/or polyelectrolyte, being thereafter    rinsed and/or dried, the first coat being contacted into a second    aqueous composition in the form of a solution, emulsion and/or    suspension, in particular in a dipping process, where the ions,    complexes and/or compounds of the first coat are able optionally to    diffuse into the second aqueous composition and/or to enter into    interaction and/or into reaction, preferably precipitation reaction    and/or salting-out reaction, and/or    -   wherein the first coat is optionally at least partly dissolved,        it not being absolutely necessary for substance of the first        coat to be taken up into the new coating, but being taken up in        many outcomes, with the second aqueous composition optionally        comprising at least one precipitable substance, at least one        kind of depositable particles and/or at least one depositable        compound, which optionally enter into a precipitation reaction        and/or salting-out reaction with the ions, complexes and/or        compounds of the first coat,    -   wherein a second coat (precipitation coat, secondary coat),        optionally comprising precipitated and/or deposited substances,        is formed on the first coat and/or in place of the first coat,        and is thereafter rinsed, dried and/or further-coated, there        being, overall, at least one-fold drying and/or treatment at a        temperature in particular in the range from 10 to 170° C. and/or        chemically, in order to apply and/or fix the substances on the        substrate, and the dry film formed, comprising the first and        second coats, has a thickness of at least 1 μm or 2 μm.-   B) Method for coating surfaces of substrates which may optionally    have been precoated (=surfaces to be coated) with a first aqueous    composition in the form of a solution, a colloidal solution,    emulsion and/or suspension which comprises at least one permanently    cationic and/or latently cationic organic polymer and/or copolymer,    which is in solution in water and has a chain, a backbone and/or a    dendrimer based on polyethyleneimine, polyvinylamine and/or    chitosan, and/or derivatives thereof and/or modifications thereof,    wherein a first coat (activating coat) is formed which comprises at    least one permanently cationic and/or latently cationic polymer    and/or copolymer, wherein the first coat is thereafter rinsed and/or    dried, wherein the first coat is contacted with a second aqueous    composition, which in particular is a solution or is in colloidal    form, in particular in a dipping process, wherein the first coat is    optionally at least partly dissolved and/or detached and/or wherein    the ions, complexes and/or compounds of the first coat are able    optionally to diffuse at least partly in each case into the second    aqueous composition, to be incorporated therein and/or to enter    therewith into interaction, especially electrostatic and/or    complex-forming interaction, and/or into reaction, preferably    precipitation reaction and/or salting-out reaction, and/or wherein    the first coat is optionally at least partially dissolved, with    optionally at least one substance of the first coat being taken up    into the new coating, wherein the second aqueous composition    optionally comprises at least one precipitable substance, at least    one kind of depositable particles and/or at least one depositable    compound which enters optionally into a precipitation reaction    and/or salting-out reaction with the ions, complexes and/or    compounds of the first coat, wherein a second coat comprising    precipitated and/or deposited substances is formed on the first coat    and/or, after at least partial dissolution and/or detachment of the    first coat, on the surfaces that are to be coated or on the    remainder of the first coat, and which is thereafter rinsed, dried    and/or further-coated, there being, overall, at least one-fold    drying and/or treatment at a temperature in particular in the range    from 10 to 170° C., physically and/or chemically, in order to form    and/or fix the substances on the surfaces to be coated, in a coat or    in a coat sequence.-   C) Method according to one of the preceding variants, wherein the    activating coat is generated by means of dip coating.-   D) Aqueous composition which comprises at least one permanently    cationic and/or latently cationic organic polymer and/or copolymer    which is in solution in water and which has a chain, a backbone    and/or a dendrimer based on polyethyleneimine, polyvinylamine and/or    chitosan, and/or derivatives thereof and/or modifications thereof.-   E) Use of a method for electroless coating according to any of    variants A) to C) for the coating of strips, sheets, profiles, parts    and/or for the production of vehicle components, of architectural    components, vehicle bodies, and household appliances.-   F) Use of a composition according to variant D for the coating of    strips, sheets, profiles, parts and/or for the production of vehicle    components, of architectural components, vehicle bodies, and    household appliances.

Substrates employed, accordingly, for the purposes of the presentinvention include more particularly strips, sheets, profiles, partspreferably for the production of vehicle components, of architecturalcomponents, vehicle bodies, and components for household appliances.

Other variants of the present invention are as follows:

-   V1. Method for electroless coating of substrates, comprising or    consisting of the following steps:    -   I. provision of a substrate,    -   II. optional cleaning of the substrate,    -   III. application of an activating coat,    -   IV. optional intermediate drying of the activating coat,    -   V. rinsing of the activating coat,    -   VI. coating of the activated surfaces with formulations and/or        dispersions for forming an organic secondary coating,    -   VII. rinsing of the secondary coating,    -   VIII. drying and/or crosslinking of the coating,    -   characterized in that the activating coat is formed from a        substance or mixture of substances selected from the group        consisting of polyethyleneimine, silane-modified        polyethyleneimine, polyethyleneimine modified with silane        compound(s), polyvinylamine, silane-modified polyvinylamine,        polyvinylamine modified with silane compound(s), chitosan,        silane-modified chitosan, chitosan modified with silane        compound(s), and mixtures thereof,    -   with the proviso that when using unmodified polyethyleneimine        the intermediate drying IV. is obligatory    -   or characterized in that the activating coat is formed from a        substance or mixtures of substances selected from the group        consisting of chitosan, calcium acetate, calcium formate, and        mixtures thereof.-   V2. Method according to V1, characterized in that step III. the    activating coat is formed from a substance or mixture of substances    selected from the group consisting of silane-modified    polyethyleneimine, polyethyleneimine modified with silane    compound(s), polyvinylamine, silane-modified polyamine,    polyvinylamine modified with silane compound(s), chitosan,    silane-modified chitosan, chitosan modified with silane compound(s),    and mixtures thereof.-   V3. Method according to V1 or V2, characterized in that in step I. a    metallic substrate selected from the group consisting of aluminum,    iron, copper, titanium, zinc, tin and/or alloys and/or mixtures    thereof is used, preferably consisting of steel, copper, aluminum,    alloys therewith or thereof, more preferably consisting of steel or    aluminum.-   V4. Method according to any of variants V1 to V3, characterized in    that in step VI. the formulations and/or dispersions for forming an    organic secondary coating are selected from the group consisting of    -   A) anionically stabilized aqueous polymer particle dispersions,    -   B) anionically stabilized aqueous formulations,    -   and mixtures thereof.-   V5. Method according to any of variants V1 to V4, characterized in    that polysiloxanes are used as modifying silane compounds.-   V6. Method according to any of variants V1 to V5, characterized in    that the activating agent has been prepared by reaction of silane    and/or silane compounds and polyethyleneimine in a ratio of 1:1.-   V7. Use of polyethyleneimine, polyvinylamine and/or chitosan as    activating agents in methods for electroless coating of substrates,    more particularly metallic substrates.-   V8. Use according to V7, characterized in that polyethyleneimine,    polyvinylamine and/or chitosan have been modified with silane and/or    silane compounds.-   V9. Use according to V8 of an activating agent modified with silane    and/or silane compounds, characterized in that the activating agent    has been prepared by reaction of silane and/or silane compounds and    polyethyleneimine in a ratio of 1:1.-   V10. Method for electroless coating of substrates, comprising or    consisting of the following steps:    -   I. provision of a substrate,    -   II. optional cleaning of the substrate,    -   III. application of an activating coat,    -   IV. optional intermediate drying of the activating coat,    -   V. rinsing of the activating coat,    -   VI. coating of the activated surfaces with formulations and/or        dispersions for forming an organic secondary coating,    -   VII. rinsing of the secondary coating,    -   VIII. drying and/or crosslinking of the coating,    -   characterized in that the activating coat is formed from one or        more anionic polyelectrolytes selected from the group consisting        of polyacrylic acid, silane-modified polyacrylic acid,        polyacrylic acid modified with silane compound(s), polyacrylic        acid-maleic acid copolymer, silane-modified polyacrylic        acid-maleic acid copolymer, polyacrylic acid-maleic acid        copolymer modified with silane compound(s), polyacrylic        acid-acrylamide copolymer, silane-modified polyacrylic        acid-acrylamide copolymer, polyacrylic acid-acrylamide copolymer        modified with silane compound(s), polystyrenesulfonic acid,        polyvinylsulfonic acid, polyphosphoric acid, and mixtures        thereof.-   V11. Method according to V10, characterized in that in step III. the    activating coat consists of a substance or mixture of substances    selected from the group consisting of polyacrylic acid,    silane-modified polyacrylic acid, polyacrylic acid modified with    silane compound(s), polyacrylic acid-maleic acid copolymer,    silane-modified polyacrylic acid-maleic acid copolymer, polyacrylic    acid-maleic acid copolymer modified with silane compound(s),    polyacrylic acid-acrylamide copolymer, silane-modified polyacrylic    acid-acrylamide copolymer, polyacrylic acid-acrylamide copolymer    modified with silane compound(s), and mixtures thereof,    -   preferably from the group consisting of silane-modified        polyacrylic acid, polyacrylic acid modified with silane        compound(s), silane-modified polyacrylic acid-maleic acid        copolymer, polyacrylic acid-maleic acid copolymer modified with        silane compound(s), silane-modified polyacrylic acid-acrylamide        copolymer, polyacrylic acid-acrylamide copolymer modified with        silane compound(s), and mixtures thereof.-   V12. Method according to V10 or V11, characterized in that in    step I. a metallic substrate selected from the group consisting of    aluminum, iron, copper, titanium, zinc, tin and/or alloys and/or    mixtures thereof is used, preferably consisting of steel, copper,    aluminum, alloys therewith or thereof, more preferably consisting of    steel or aluminum.-   V13. Method according to any of variants V10 to V12, characterized    in that in step VI. the formulations and/or dispersions for forming    an organic secondary coating are selected from the group consisting    of    -   A) cationically stabilized aqueous polymer particle dispersions,    -   B) cationically stabilized aqueous formulations,    -   and mixtures thereof.-   V14. Method according to any of variants V10 to V13, characterized    in that polysiloxanes are used as modifying silane compounds.-   V15. Use of polyacrylic acid, silane-modified polyacrylic acid,    polyacrylic acid modified with silane compound(s), polyacrylic    acid-maleic acid copolymer, silane-modified polyacrylic acid-maleic    acid copolymer, polyacrylic acid-maleic acid copolymer modified with    silane compound(s), polyacrylic acid-acrylamide copolymer,    silane-modified polyacrylic acid-acrylamide copolymer, polyacrylic    acid-acrylamide copolymer modified with silane compound(s),    polystyrenesulfonic acid, polyvinylsulfonic acid, polyphosphoric    acid and mixtures thereof, preferably polyacrylic acid,    silane-modified polyacrylic acid, polyacrylic acid modified with    silane compound(s), polyacrylic acid-maleic acid copolymer,    silane-modified polyacrylic acid-maleic acid copolymer, polyacrylic    acid-maleic acid copolymer modified with silane compound(s),    polyacrylic acid-acrylamide copolymer, silane-modified polyacrylic    acid-acrylamide copolymer, polyacrylic acid-acrylamide copolymer    modified with silane compound(s), and mixtures thereof as activating    agent in methods for electroless coating of substrates, more    particularly metallic substrates.-   V16. Method for electroless coating of substrates, comprising or    consisting of the following steps:    -   I. provision of a substrate,    -   II. optional cleaning of the substrate,    -   III. application of an activating coat,    -   IV. optional intermediate drying of the activating coat,    -   V. rinsing of the activating coat,    -   VI. coating of the activated surfaces with formulations and/or        dispersions for forming an organic secondary coating,    -   VII. rinsing of the secondary coating,    -   VIII. drying and/or crosslinking of the coating,    -   characterized in that    -   the polyelectrolytes of the secondary coating, either completely        or to an extent of at least 80% by weight, preferably at least        90% by weight, have the same charge sign as the activating        agents used in step III.-   V17. Method according to variant V16, characterized in that    -   a) chitosan, calcium acetate, calcium formate, or mixtures        thereof is or are used as cationic activating agent.-   V18. Method according to variant V16, characterized in that    -   b) polyacrylic acid and/or polyphosphoric acid are or is used as        anionic activating agent.

The various embodiments of the present invention, for example but notexclusively those of the various dependent claims, may be combined withone another in any desired way.

Inventive Examples (B) and Comparative Examples (VB) Examples B48 to B58on the Use of Similarly Charged Activating Coats and Substances for aSecondary Coat

These fundamental experiments serve to show that a cationic activatingagent is also able to precipitate a cationically stabilized dispersionand that an anionic activating agent is also able to precipitate ananionically stabilized dispersion. Fundamentally the same productionoperation was used under the same conditions as for the modifiedpolyelectrolytes.

In the course of these experiments it was possible, surprisingly, toshow that an activating coat whose activating substances have similarcharges to the substances of the aqueous composition for forming thesecondary coat, for precipitating, for salting out and/or fordepositing, and also for forming a secondary coat, is virtuallyidentical to that in the case of an activating coat which is oppositelycharged relative to the substances of the aqueous composition forforming the secondary coat and relative to precipitations and forforming a secondary coat. In this case, however, no dry film was formedin the case of the secondary coat, and so it was not possible to measureany dry film thicknesses.

Nevertheless it was possible to show in principle, with these initialexperiments, that an activating coat may also serve successfully forsimilarly charged substances of the aqueous composition for forming thesecondary coat. The precipitation experiments indicate that sufficientdry film thicknesses of the secondary coat can be generated, with,preferably, substances having chemical affinity being selected in eachcase and being combined in the method of the invention.

Table 1 for Cationic-Cationic Treatment with Examples B48 to B52:Cationic Activating Agent with Cationically Stabilized Dispersion

Example B48 B49 B50 B51 B52 Cationic activating agent Type No. 1 2 13 1516 Cationically stabilized dispersion Type No. (conc. %) 21 (20) 21 (20)21 (20) 21 (20) 21 (20) Precipitation intensity Strong X X X Weak XAlmost no precipitation XTable 2 for Anionic-Anionic Treatment with Examples B53 to B58: AnionicActivating Agent with Anionically Stabilized Dispersion

Example B53 B54 B55 B56 B57 B58 Anionic activating agent Type No. 21 2225 26 28 30 Anionically stabilized dispersion Type No. 1 (20) 1 (20) 1(20) 1 (20) 1 (20) 1 (20) (conc. %) Precipitation intensity Strong X XWeak X X Almost no X X precipitation Strong: Activating agentprecipitates 61-100% of the dispersion. Weak: Activating agentprecipitates 11-60% of the dispersion. Almost no precipitation: agentprecipitates 0-10 percent of the dispersion. The values were determinedin each case gravimetrically.

Examples B61 to B120 for Anionic Polyelectrolytes as Activating Agents

I. Substrate Type (Metal Sheets):

-   1: Electrolytically galvanized steel sheet with a zinc coat add-on    of 5 μm, sheet thickness 0.81 mm.-   2: Hot-dip-galvanized steel sheet, sheet thickness about 0.8 mm.-   3: Cold-rolled steel, sheet thickness about 0.8 mm.-   4: Aluminum alloy of quality class AC 170, sheet thickness about 1.0    mm.    II. Alkaline Cleaning:-   1: 30 g/L alkaline, silicate-free cleaner Gardoclean®S 5176 and also    4 g/L Gardobond®Additive H 7406 for suppressing foaming during    spraying, from Chemetall GmbH, were prepared in municipal water for    a pH of 10.5, giving only a moderate pickling attack. The sheets    were cleaned by spraying at 60° C. for 180 seconds, and then rinsed    for 120 seconds with municipal water and thereafter for 120 seconds    with deionized water, by dipping.    III. Activation:

Activation is used to apply a homogeneous secondary coat, with theaqueous activating agent comprising the substances required forprecipitation, coagulation, salting-out and/or deposition, and/orconsisting, besides water, of the substances below. Coating took placewith the following activating agents, with the cleaned substrates havingbeen immersed in a gently agitated bath over 2.5 minutes at roomtemperature:

-   21: Anionic polyacrylic acid. Average molecular weight 4 000 g/Mol.    Amount of solids and active ingredients: 2% by weight.-   22: Anionic polyacrylic acid. Average molecular weight 250 000    g/Mol. Amount of solids and active ingredients: 2% by weight.-   23: Anionic polyacrylic acid. Average molecular weight in the order    of 5000 g/mol. Amount of solids and active ingredients: 2% by    weight.-   24: Anionic polyacrylic acid-maleic acid copolymer. Average    molecular weight 3000 g/mol. Amount of solids and active    ingredients: 2% by weight.-   25: Anionic polyacrylic acid-maleic acid copolymer. Average    molecular weight 70 000 g/mol. Amount of solids and active    ingredients: 2% by weight.-   26: Anionic polyacrylic acid-acrylamide copolymer from    Sigma-Aldrich. Average molecular weight 520 000 g/mol. Amount of    solids and active ingredients: 2% by weight.-   27: Polystyrenesulfonic acid from Sigma-Aldrich. Average molecular    weight 70 000 g/mol. Amount of solids and active ingredients: 2% by    weight.-   28: Polystyrenesulfonic acid from Sigma-Aldrich. Average molecular    weight 100 000 g/mol. Amount of solids and active ingredients: 2% by    weight.-   29: Polyvinylsulfonic acid from Sigma-Aldrich. Amount of solids and    active ingredients: 2% by weight. Molecular weight in the order of    1000 to 50 000 g/mol.-   30: Polyphosphoric acid from Sigma-Aldrich. Amount of solids and    active ingredients: 2% by weight. Molecular weight in the order of    500 to 800 000 g/mol.-   31: Anionic polyacrylic acid modified with silane groups and having    an average molecular weight of 4000 g/mol, in adapted pretreatment    solution based on Oxsilan® from Chemetall GmbH. Amount of solids and    active ingredients: 2% by weight.-   32: Anionic polyacrylic acid modified with silane groups and having    an average molecular weight of 250 000 g/mol in adapted pretreatment    solution based on Oxsilan® from Chemetall GmbH. Amount of solids and    active ingredients: 2% by weight.-   32 blade-coated: The necessary coat thickness of activator 32 was    applied to the substrates in a controlled way by means of    doctor-blade application. Amount of solids and active ingredients:    2% by weight.-   33: Anionic polyacrylic acid modified with silane groups and having    an average molecular weight in the order of 5000 g/mol, in adapted    pretreatment solution based on Oxsilan® from Chemetall GmbH. Amount    of solids and active ingredients: 2% by weight.-   34: Anionic polyacrylic acid-maleic acid copolymer modified with    silane groups and having an average molecular weight of 3000 g/mol,    in adapted pretreatment solution based on Oxsilan® from Chemetall    GmbH. Amount of solids and active ingredients: 2% by weight.-   35: Anionic polyacrylic acid-maleic acid copolymer modified with    silane groups and having an average molecular weight of 70 000    g/mol, in adapted pretreatment solution based on Oxsilan® from    Chemetall GmbH. Amount of solids and active ingredients: 2% by    weight.-   36: Anionic polyacrylic acid-acrylamide copolymer modified with    silane groups and having an average molecular weight of 520 000    g/mol, in adapted pretreatment solution based on Oxsilan® from    Chemetall GmbH.

Amount of solids and active ingredients: 2% by weight.

IV. Intermediate Drying of the Activating Coat:

In the course of the experiments it was found that an intermediatedrying step may possibly have an influence on the thickness of thesecondary coat, since smaller amounts of the activating coat wereremoved in the subsequent rinsing step V. after an intermediate dryingthan in the case of rinsing without previous intermediate drying.

-   1: Drying at 40° C. for 15 minutes in a drying cabinet with forced    air and fresh-air supply.    V. Rinsing of the Activating Coat:

Rinsing was carried out once at room temperature over 2 minutes by slowimmersion into a gently agitated bath with deionized water.

Since part of the fresh activating coat is rinsed off in the course ofthe rinsing operation, the remaining amounts of the activating coat areascertained, together with element amounts of the remainders of cleaningagents, and optionally of a pretreatment coat and/or primer coat, etc.It proved advantageous if as high as possible a fraction of theactivating coat is retained during rinsing.

The amounts of elements in the activating coat were determined by meansof X-ray fluorescence analysis (XFA) for the activating coat, includingthe amounts from previous treatments—where present. The figures relateto the element contents after rinsing. With these figures it is possibleto estimate the remaining coat thicknesses and to compare them fromsample to sample, it being made clear that in spite of intensiverinsing, comparatively high fractions of the activating coat areretained. These amounts are sufficient to provide the activated surfacewith effective preparation for the subsequent treatment steps VI. andVII.

Parallel investigations by scanning electron microscopy (SEM) make itclear that impervious coatings are formed from the combination of thecontacting with activating agent and subsequent coating with the aqueouscomposition for the secondary coat.

VI. Coating of the Activated Surfaces with Aqueous Formulations orDispersions for Forming the Secondary Coat:

Different kinds of aqueous formulations and dispersions for contactingand/or coating these metal sheets were prepared. The secondary coat wasformed by dipping the coated substrate into a gently agitated bath ofthe dispersion or formulation at room temperature for 5 minutes in eachcase.

A) Cationically Stabilized Aqueous Polymer Particle Dispersions:

-   21 (30): Cationically stabilized dispersion A. Average particle size    d₅₀ 113 nm. Viscosity<200 mPa·s. pH 6. Amount of solids and active    ingredients 30% by weight.-   21 (20): Cationically stabilized dispersion A. Average particle size    d₅₀ 113 nm. Viscosity<200 mPa·s. pH 6. Amount of solids and active    ingredients 20% by weight.-   21 (10): Cationically stabilized dispersion A. Average particle size    d₅₀ 113 nm. Viscosity<200 mPa·s. pH 6. Amount of solids and active    ingredients 10% by weight.-   22 (30): Cationically stabilized dispersion B. Average particle size    d₅₀ 200 nm. Viscosity<200 mPa·s. pH 6. Amount of solids and active    ingredients 30% by weight.-   22 (20): Cationically stabilized dispersion B. Average particle size    d₅₀ 200 nm. Viscosity<200 mPa·s. pH 6. Amount of solids and active    ingredients 20% by weight.-   22 (10): Cationically stabilized dispersion B. Average particle size    d₅₀ 200 nm. Viscosity<200 mPa·s. pH 6. Amount of solids and active    ingredients 10% by weight.-   23 (20): Cationically stabilized polyurethane dispersion C with    quaternary ammonium groups. Average particle size d₅₀ 230 nm.    Viscosity 1-1500 mPa·s. pH 2-6. Amount of solids and active    ingredients 20% by weight.-   24 (20): Cationically stabilized polyacrylate dispersion D. Average    particle size d₅₀ 200 nm. Viscosity 20-200 mPa·s. pH 7-8. Amount of    solids and active ingredients 20% by weight.-   25 (20): Cationically stabilized polyacrylate dispersion E. Average    particle size d₅₀ 84 nm. Viscosity<200 mPa·s. pH 8. Amount of solids    and active ingredients 20% by weight.-   26 (20): Cationically stabilized polyacrylate dispersion F. Average    particle size d₅₀ 117 nm. Viscosity<200 mPa·s. pH 8. Amount of    solids and active ingredients 20% by weight.    B) Cationically Stabilized Aqueous Formulations:-   27 (20): One-component, cationically stabilized deposition paint    formulation. Film-forming parameters 175° C., 15 min. pH 5.8. Amount    of solids and active ingredients 20% by weight.-   27 (10): One-component, cationically stabilized deposition paint    formulation. Film-forming parameters 175° C., 15 min. pH 5.8. Amount    of solids and active ingredients 10% by weight.-   28 (20): One-component, cationically stabilized deposition paint    formulation. Film-forming parameters 175° C., 15 min. pH 5.5. Amount    of solids and active ingredients 20% by weight.-   28 (10): One-component, cationically stabilized deposition paint    formulation. Film-forming parameters 175° C., 15 min. pH 5.5. Amount    of solids and active ingredients 10% by weight.    VII. Rinsing of the Secondary Coat:

The purpose of rinsing after the secondary coat is to removeuncoagulated and/or precipitated constituents of the formulation andaccumulations of the formulation, and to make the procedure as close inreality as possible to the usual procedure in the automobile industry.The reason is that in the automobile industry, at least one rinsing withwater usually takes place, mostly either by dip rinsing or sprayrinsing. Rinsing of the secondary coat was carried out once for 2minutes in each case at room temperature with deionized water and thesubstrates coated with a secondary coat were dipped, without priordrying of the secondary coat, into a gently agitated bath.

VIII. Drying, Filming and/or Crosslinking of the Secondary Coat:

Drying or drying with filming in particular of the organic polymericconstituents:

-   1: Dried at 175° C., 15 minutes in a drying cabinet with forced air    and fresh-air supply.

Drying was carried out with filming, since at the high temperatures allexamples gave a dry film which under the scanning electronmicroscope canno longer be resolved as a particulate coating.

Parallel investigations by scanning electronmicroscopy (SEM) made itclear that in accordance with the invention, coatings were formed which,owing to the combination of contacting with activating agent, rinsing,and coating of the activated surfaces that remained with an aqueouscomposition, more particularly in the form of dispersions and/orformulations, it was possible to form impervious coatings which oftenhave a dry film thickness in the range from 3 to 7 μm. The dry filmthicknesses are indeed much lower than for those activated with cationicpolyelectrolyte, but had not yet been developed for so long and soextensively as those activated with anionic polyelectrolyte.Accordingly, a distinct rise in the dry film thicknesses in furtherdevelopment operations is expected. The electron micrographsconsistently showed homogeneous secondary coats, thus indicating areliable, self-regulating, and readily controllable coating method.

If a secondary coat was formed on a thin activating coat which was nothomogeneous and not impervious, the secondary coat, though thinner, wasnevertheless formed homogeneously and imperviously. In certain of theexperiments, coating took place only within a time of 2 or 3 minutes,although the selected 5-minute treatment time was retained, thus givingan end state of the secondary coat in 5 minutes' treatment time. Thesecondary coat formed was first rinsed and only thereafter dried. Therinsing of the secondary coat was used for removing excess substance ofthe aqueous composition, and impurities. Here it was ensured that thesecondary coat has a few minutes' time prior to rinsing, within thetreatment time, to allow satisfactory saturation of the polyelectrolytewith the organic matrix. In all of the experiments, 5 minutes weresufficient for this purpose. It is assumed that within this time thepolyelectrolyte is enveloped with polymer, so that the secondary coat isformed rinse-resistantly. It was found that the secondary coatscomprising modified polyelectrolyte were significantly morerinse-resistant than the secondary coats comprising unmodifiedpolyelectrolyte. Nevertheless, the secondary coats comprising unmodifiedpolyelectrolyte were sufficiently rinse-resistant for these experiments.Accordingly, the conditions are met to allow an electrodepositioncoating process to be converted to an electroless process. Initialcorrosion tests and adhesion tests demonstrate that the corrosionresistance and the paint adhesion of the coat system of the inventionare within an order of magnitude fundamentally sufficient for thetechnical purpose. In the wide variety of experiments, it was possibleto form secondary coats with dry film thicknesses of only up to 7 μm in5 minutes' treatment time in each case. As a result, it is possible, inan environmentally friendly way, to avoid high energy quantities and acostly and inconvenient plant engineering.

In comparison of the use of anionic polyelectrolytes with the use ofcationic polyelectrolytes, with cationic salts and with anionic salts,there were no fundamental differences, but quantitative differences werefound in the dry film thicknesses, and preferably, in each case,substances with chemical affinity are selected and are combined in themethod of the invention.

In the case of the anionic polyelectrolytes as activating agents it wasfound that the secondary coats of modified polyelectrolyte weresignificantly more rinse-resistant than the secondary coats comprisingunmodified polyelectrolyte. Nevertheless, the secondary coats comprisingunmodified polyelectrolyte were sufficiently rinse-resistant for theseexperiments. The conditions and the tendencies to form very thicksecondary coats that were found were the same as those described in theexamples and in relation to the figures with cationic polyelectrolytes.Here as well, therefore, the conditions are met to allow a switch froman electric deposition coating process to an electroless process.

Here as well, initial corrosion tests and adhesion tests demonstratethat the corrosion resistance and the paint adhesion of the layersequence of the invention are within an order of magnitude which issufficient in principle for the technical purpose.

Tables for Examples B61-B120:

TABLE 13 Examples B61-B90 with unmodified anionic polyelectrolytes andwith intermediate drying according to the concentration of theactivating agent Example B61 B62 B63 B64 B65 B66 B67 B68 B69 B70Substrate type No.: 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 Alkalinecleaning No.: 1 1 1 1 1 1 1 1 1 1 Activation Activating agent No.: 21 22  23  24  25  26  27  28  29  30  Intermediate drying of theactivating coat: Drying No.: 1 1 1 1 1 1 1 1 1 1 Properties afterrinsing of the activating coat: Rinse resistance yes yes yes yes yes yesyes yes yes yes SEM coat thickness dry 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.20.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 film [μm] Secondary coatFormulation/ n(30); n(30); Dispersion No. n = 1.2 n = 1.2 Rinsing of thesecondary coat Rinse resistance: yes yes yes yes yes yes yes yes yes yesDrying/crosslinking of the coat Drying No.: 1 1 1 1 1 1 1 1 1 1 SEM coatthickness dry 5-6 1-2 1-2 0.5-1   6-7 0.5-1   0.1-0.5 — 1-2 3-5 film[μm] Example B71 B72 B73 B74 B75 B76 B77 B78 B79 B80 Substrate type No.:1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 Alkaline cleaning No.: 1 1 1 1 11 1 1 1 1 Activation Activating agent No.: 21  22  23  24  25  26  27 28  29  30  Intermediate drying of the activating coat: Drying No.: 1 11 1 1 1 1 1 1 1 Properties after rinsing of the activating coat: Rinseresistance yes yes yes yes yes yes yes yes yes yes SEM coat thicknessdry 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2-0.1-0.2 0.1-0.2 film [μm] Secondary coat Formulation/ n(20); n = 1-8Dispersion No. Rinsing of the secondary coat Rinse resistance: yes yesyes yes yes yes yes yes yes yes Drying/crosslinking of the coat DryingNo.: 1 1 1 1 1 1 1 1 1 1 SEM coat thickness dry 5-6 3-4 3-4 1-2 4-5  1-1.5 0.5-0.8 — 2-3 6-8 film [μm] Example B81 B82 B83 B84 B85 B86 B87B88 B89 B90 Substrate type No.: 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4Alkaline cleaning No.: 1 1 1 1 1 1 1 1 1 1 Activation Activating agentNo.: 21  22  23  24  25  26  27  28  29  30  Intermediate drying of theactivating coat: Drying No.: 1 1 1 1 1 1 1 1 1 1 Properties afterrinsing of the activating coat: Rinse resistance yes yes yes yes yes yesyes yes yes yes SEM coat thickness dry 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.20.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 0.1-0.2 film [μm] Secondary coatFormulation/ n(10); n = 1, 2, 7, 8 Dispersion No. Rinsing of thesecondary coat Rinse resistance: yes yes yes yes yes yes yes yes yes yesDrying/crosslinking of the coat Drying No.: 1 1 1 1 1 1 1 1 1 1 SEM coatthickness dry 3-4 3-4 3-4 2-3 3-4 1-2 1-2 — 5-6 15-16 film [μm]

TABLE 14 Verification of the rinse resistance of the modified anionicpolyelectrolyte activation without intermediate drying in the case ofexamples B91-B97 Example B91 B92 B93 B94 B95 B96 B97 Substrate type No.:1-4 1-4 1-4 1-4 1-4 1-4 1-4 Alkaline cleaning No.: 1 1 1 1 1 1 1Activation Activating agent No.: 31  32  33  34  35  36  37 Intermediate drying of the activating coat: Drying No.: — — — — — — —Properties after rinsing of the activating coat: Rinse resistance yesyes yes yes yes yes yes SEM coat thickness dry film 0.05-0.1  0.05-0.1 0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1  [μm] Secondary coatFormulation/ — — — — — — — Dispersion No. Rinsing of the secondary coatRinse resistance: — — — — — — — Drying/crosslinking of the coat DryingNo.: — — — — — — — SEM coat thickness dry film — — — — — — — [μm]

TABLE 15 Examples B98-B115 with modified anionic polyelectrolyteswithout intermediate drying according to concentration of the activatingagent Example B98 B99 B100 B101 B102 B103 B104 B105 B106 Substrate typeNo.: 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 Alkaline cleaning No.: 1 1 1 11 1 1 1 1 Activation Activating agent No.: 31  32  33  34  35  36  31 32  33  Intermediate drying of the activating coat: Drying No.: 1 1 1 11 1 1 1 1 Properties after rinsing of the activating coat: Rinseresistance yes yes yes yes yes yes yes yes yes SEM coat thickness dry0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1 0.05-0.1  0.05-0.1  film [μm] Secondary coat Formulation/ n(30); n = 1,2 n(20); n = 1-8 Dispersion No. Rinsing of the secondary coat Rinseresistance yes yes yes yes yes yes yes yes yes Drying/crosslinking ofthe coat Drying No.: 1 1 1 1 1 1 1 1 1 SEM coat thickness dry 3-4 1-21-2 0.5-1 5-6 0.5-1 3-4 3-4 2-4 film [μm] Example B107 B108 B109 B110B111 B112 B113 B114 B115 Substrate type No.: 1-4 1-4 1-4 1-4 1-4 1-4 1-41-4 1-4 Alkaline cleaning No.: 1 1 1 1 1 1 1 1 1 Activation Activatingagent No.: 34  35  36  31  32  33  34  35  36  Intermediate drying ofthe activating coat: Drying No.: 1 1 1 1 1 1 1 1 1 Properties afterrinsing of the activating coat: Rinse resistance yes yes yes yes yes yesyes yes yes SEM coat thickness dry 0.05-0.1  0.05-0.1  0.05-0.1 0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1  0.05-0.1  film [μm]Secondary coat Formulation/ n(20); n = 1-8 n(10); n = 1, 2, 7, 8Dispersion No. Rinsing of the secondary coat Rinse resistance yes yesyes yes yes yes yes yes yes Drying/crosslinking of the coat Drying No.:1 1 1 1 1 1 1 1 1 SEM coat thickness dry 1-2 4-5 1-2 3-4 3-4 3-4 3-4 4-53-4 film [μm]

TABLE 16 Examples B116-B117 for demonstrating the correlation of the dryfilm thicknesses of the activating coat and of the secondary coatExample B116 B117 Substrate type No.: 1, 2 1, 2 Alkaline cleaning No.: 11 Activation Activating agent No.: 32 (blade-coated) 32 (blade-coated)Intermediate drying of the activating coat: Drying No.: 1 1 Propertiesafter rinsing of the activating coat: Rinse resistance yes yes SEM coatthickness dry film [μm] 0.2 0.4 Secondary coat Formulation/dispersionNo.: n(20); n = 1-8 Rinsing of the secondary coat Rinse resistance: yesyes Drying/crosslinking of the coat Drying No.: 1 1 SEM coat thicknessdry film [μm] 3-4 7-8

TABLE 17 Formation of thicker secondary coats with less concentratedaqueous compositions for forming secondary coats in the case of examplesB118-B120 Example B118 B119 B120 Substrate type No.: 1-4 1-4 1-4Alkaline cleaning No.: 1 1 1 Activation Activating agent No.: 31  31 31  Intermediate drying of the activating coat: Drying No.: 1 1 1Properties after rinsing of the activating coat: Rinse resistance yesyes yes SEM coat thickness dry film [μm] 0.1-0.2 0.1-0.2 0.1-0.2Secondary coat Formulation/dispersion No.: n(30); n(20); n(10); n = 1, 2n = 1, 2 n = 1, 2 Drying/crosslinking of the coat Rinse resistance: yesyes yes Drying/crosslinking of the coat Drying No.: 1 1 1 SEM coatthickness dry film [μm] 4-5 5-6 9-10Tables for Comparative Examples VB121-VB130:

TABLE 18 Verification that without an activating coat no secondary coatis formed (no viscosity effect) in the case of comparative examplesVB121-VB128 Example VB121 VB122 VB123 VB124 VB125 VB126 VB127 VB128Substrate type No.: 1-4 1-4 1-4 1-4 1-4 1-4 1-4 1-4 Alkaline cleaningNo.: 1 1 1 1 1 1 1 1 Activation Activating agent No.: — — — — — — — —Intermediate drying of the activating coat: Drying No.: — — — — — — —Properties after rinsing of the activating coat: Rinse resistance — — —— — — — — SEM coat thickness dry — — — — — — — — film [μm] Secondarycoat Formulation/dispersion No.: 1(30) 2(30) 3(20) 4(20) 5(20) 6(20)7(20) 8(20) Drying/crosslinking of the coat Rinse resistance: no no nono no no no no Drying/crosslinking of the coat Drying No.: 1 1 1 1 1 1 11 SEM coat thickness dry 0 0 0 0 0 0 0 0 film [μm]

TABLE 19 Maximum achievable dry film thicknesses with the technology ofWO 2010/054985 A1 in the case of comparative examples VB129-VB130Example VB129 VB130 Substrate type No.: 1, 2 1, 2 Alkaline cleaning No.: 1  1 Activation Activating agent No.: 23 24 Intermediate drying of theactivating coat: Drying No.: — — Properties after rinsing of theactivating coat: Rinse resistance yes yes XFA element amounts mg/m²: Si4-7 5-9 Ti <1 <1 Zr 15-20 15-21 Mn <1 <1 SEM coat thickness dry film[μm] — — Secondary coat Formulation/dispersion No.: n(20); n = 1, 2, 7,8 Rinsing of the secondary coat Rinse resistance yes yesDrying/crosslinking of the coat Drying No.:  1  1 SEM coat thickness dryfilm [μm] 0.2-0.3 0.1-0.2

The invention claimed is:
 1. A method for coating a substrate, themethod comprising the steps of: (I) providing a substrate; (II)optionally cleaning the substrate; (III) applying an activating coat onthe substrate; (IV) intermediate drying of the activating coat; (V)rinsing the activating coat after the intermediate drying step, whereinwhen the activating coat is rinsed at least a portion of the activatingcoat remains on the substrate; (VI) contacting and coating the remainingactivating coat on the substrate with an aqueous composition to form anorganic secondary coat, the aqueous composition in at least one formselected from the group consisting of a solution, an emulsion, asuspension, and mixtures thereof; (VII) optionally rinsing the organicsecondary coat; and (VIII) optionally drying the organic secondary coat;wherein the activating coat is formed from one or more anionicpolyelectrolytes selected from the group consisting of polyacrylic acid,silane-modified polyacrylic acid, polyacrylic acid modified with silanecompound(s), polyacrylic acid-maleic acid copolymer, silane-modifiedpolyacrylic acid-maleic copolymer, polyacrylic acid-maleic acidcopolymer modified with silane compound(s), polyacrylic acid-acrylamidecopolymer, silane-modified polyacrylic acid-acrylamide copolymer,polyacrylic acid-acrylamide copolymer modified with silane compound(s),polystyrenesulfonic acid, polyvinylsulfonic acid, polyphosphoric acid,and mixtures thereof; wherein the aqueous composition to form theorganic secondary coat has constituents which can be precipitated,deposited and/or salted out and which are anionically, zwitterionically,sterically or cationically stabilized, where anionically andcationically stabilized constituents in the aqueous composition do notadversely affect one another; wherein a dry film is formed on thesubstrate, the dry film comprising (i) the organic secondary coat or(ii) the activating coat and the organic secondary coat, and wherein thedry film has a thickness of at least about 1 μm; and wherein the coatingis electrolessly applied to the substrate.
 2. The method of claim 1,wherein the organic secondary coat is filmed and/or crosslinked.
 3. Themethod of claim 2 wherein the organic secondary coat is further coated.4. The method of claim 1, wherein the activating coat comprises amodified polyelectrolyte which has been modified with a silane, silanolor siloxane with a degree of condensation in a range from about 1 toabout
 30. 5. The method of claim 1, wherein in step (VI) the aqueouscomposition is one or more formulations and/or dispersions, selectedfrom the group consisting of the following aqueous compositions: A)anionically stabilized polymer particle dispersions, B) anionicallystabilized formulations, C) sterically stabilized polymer particledispersions, D) sterically stabilized formulations, E) zwitterionicallystabilized polymer particle dispersions, F) zwitterionically stabilizedformulations, and mixtures thereof; or selected from the groupconsisting of the following aqueous compositions: G) cationicallystabilized polymer particle dispersions, H) cationically stabilizedformulations, I) sterically stabilized polymer particle dispersions, J)sterically stabilized formulations, K) zwitterionically stabilizedpolymer particle dispersions, L) zwitterionically stabilizedformulations, and mixtures thereof.
 6. The method of claim 1, wherein instep (VI) the contacting and coating occurs in a dipping process.
 7. Themethod of claim 1, wherein in step (I) the substrate is a metallicsubstrate comprising a member selected from the group consisting ofaluminum, iron, copper, magnesium, titanium, zinc, and tin, or alloysthereof.
 8. The method of claim 7, wherein the substrate has beenprecoated or joined to a plastics component.
 9. The method of claim 1wherein the organic secondary coat is further coated.
 10. The method ofclaim 1, wherein the organic secondary coat is treated chemically and/orthermally.
 11. A method for coating of a substrate, the methodcomprising the following steps: (I) providing the substrate; (II)optionally cleaning the substrate; (III) applying an activating coat;(IV) intermediate drying the activating coat; (V) rinsing the activatingcoat after the intermediate drying step; (VI) coating the activatingcoat with one or more formulations and/or dispersions to form an organicsecondary coating; (VII) rinsing the organic secondary coating; (VIII)drying and/or crosslinking of the organic secondary coating; wherein theactivating coat is formed from one or more anionic polyelectrolytesselected from the group consisting of polyacrylic acid, silane-modifiedpolyacrylic acid, polyacrylic acid modified with silane compound,polyacrylic acid-maleic acid copolymer, silane-modified polyacrylicacid-maleic copolymer, polyacrylic acid-malic acid copolymer modifiedwith silane compound, polyacrylic acid-acrylamide copolymer,silane-modified polyacrylic acid-acrylamide copolymer, polyacrylicacid-acrylamide copolymer modified with silane compound,polystyrenesulfonic acid, polyvinylsulfonic acid, polyphosphoric acid,and mixtures thereof.